Hoo Sze Yen
Form 4 Experiments
Physics SPM 2008
CHAPTER 1: INTRODUCTION TO PHYSICS1.1 PENDULUMHypothesis: The
longer the length of a simple pendulum, the longer the period of
oscillation. Aim of the experiment: To investigate how the period
of a simple pendulum varies with its length. Variables:
Manipulated: The length of the pendulum, l Responding: The period
of the pendulum, T Constant: The mass of the pendulum bob,
gravitational acceleration Apparatus/Materials: Pendulum bob,
length of thread about 100 cm long, retort stand, stopwatch
Setup:
Thread Length, l Retort stand
Pendulum
Procedure: 1. The thread is tied to the pendulum bob. The other
end of the thread is tied around the arm of the retort stand so
that it can swing freely. The length of the pendulum, l is measured
to 80 cm as per the diagram.Chapter 1: Introduction to Physics Page
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2. With the thread taut and the bob at rest, the bob is lifted
at a small amplitude (of not more than 10). Ensure that the
pendulum swings in a single plane. 3. The time for ten complete
oscillations of the pendulum is measured using the stopwatch. 4.
Step 3 is repeated, and the average of both readings are
calculated. 5. The period of oscillation, T is calculated using the
average reading divided by the number of oscillations, i.e. 10. 6.
T2 is calculated by squaring the value of T. 7. Steps 1 to 6 are
repeated using l = 70 cm, 60 cm, 50 cm, and 40 cm. 8. A graph T2
versus l is plotted. Recording of data: Length of pendulum, l (cm)
80 70 60 50 40 Graph of T2 vs l T2 Time of oscillations, t (s) t2
Average Period of oscillation, T T = t/10 (s) T2 (s2)
t1
Length of pendulum, l
Discussion: The graph of T2 versus l shows a straight line
passing through the origin. This means that the period of
oscillation increases with the length of the pendulum, with T2
directly proportional to l. Conclusion: The longer the length of
the pendulum, the longer the period of oscillation. The hypothesis
is proven valid.
Chapter 1: Introduction to Physics
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CHAPTER 2: FORCES AND MOTION2.1 INCLINED PLANESHypothesis: The
larger the angle of incline, the higher the velocity just before
reaching the end of the runway Aim of the experiment: To study the
relationship between the velocity of motion and the angle of
inclination Variables: Manipulated: Angle of incline Responding:
Velocity just before reaching the end of the runway Constant:
Length of runway Apparatus/Materials: Trolley, protractor, wooden
blocks, cellophane tape, tickertimer, ticker tape, power supply,
friction-compensated runway Setup:
Procedure: 1. The apparatus is set up as per the diagram, and
the inclined angle of the plane is measured using a protractor. An
initial angle of 5 is used. 2. The ticker-timer is started up and
at the same time the trolley is released to slide down the plane.
3. The final velocity when the trolley reaches the end of the plane
is calculated using the distance of 10 ticks on the ticker tape. 4.
The procedure is repeated by changing the angle of incline to 10,
15, 20 and 25.
Chapter 2: Forces and Motion
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Results: Angle of incline () Final velocity (m s-1) 5 10 15 20
25 Analysis: A graph of the velocity of the trolley against the
angle of incline is plotted as follows: Velocity (m s-1)
Angle of incline () Conclusion: A higher angle of incline will
have a higher velocity at the end of the runway. Hypothesis
accepted. Note: The experiment can be modified by making the angle
constant and varying the height and length of the runway. Changes
must be made accordingly: hypothesis, variable list, procedure,
table, analysis, conclusion.
Chapter 2: Forces and Motion
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2.2 INERTIAOption 1: Using a saw bladeHypothesis: The larger the
mass, the larger the inertia Aim of the experiment: To study the
effect of mass on the inertia of an object Variables: Manipulated:
Mass, m Responding: Period of oscillation, T Constant: Stiffness of
blade, distance of the centre of the plasticine from the clamp
Apparatus/Materials: Jigsaw blade, G-clamp, stopwatch, and
plasticine spheres of mass 20 g, 40 g, 60 g, 80 g, and 100 g
Setup:
Procedure: 1. One end of the jigsaw blade is clamped to the leg
of a table with a G-clamp as per the diagram drawn. 2. A 20 g
plasticine ball is fixed at the free end of the blade. 3. The free
end of the blade is displaced horizontally and released so that it
oscillates. The time for 10 complete oscillations is measured using
a stopwatch. This step is repeated. The average of 10 oscillations
is calculated. Then, the period of oscillation is determined. 4.
Steps 2 and 3 are repeated using plasticine balls with masses 40 g,
60 g, 80 g, and 100 g. 5. A graph of T2 versus mass of load, m is
drawn.
Chapter 2: Forces and Motion
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Results: Mass of load, m (g) 20 40 60 80 100
Time of oscillations, t (s) t1 t2 Average
Period of oscillation, T T = t/10 (s) T2 (s2)
Graph of T2 versus m:
Discussion: The graph of T2 versus m shows a straight line
passing through the origin. This means that the period of
oscillation increases with the mass of the load; that is, an object
with a large mass has a large inertia. Conclusion: Objects with a
large mass have a large inertia. This is the reason why it is
difficult to set an object of large mass in motion or to stop it.
The hypothesis is valid.
Option 2: Using an inertia balanceHypothesis: The larger the
mass, the bigger the inertia Aim of the experiment: To study the
effect of mass on the inertia of an object Variables: Manipulated:
Mass, m Responding: Period of oscillation, T Constant: Stiffness of
the inertia balance Apparatus/Materials: Inertia balance, masses
for the inertia balance, G-clamp, stopwatch
Chapter 2: Forces and Motion
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Setup:
Procedure: 1. The inertia balance is set up by clamping it onto
one end of the table as shown in the figure above. 2. One mass is
placed into the inertia balance. The inertia balance is displaced
to one side so that it oscillates in a horizontal plane. 3. The
time for 10 complete oscillations is measured using a stopwatch.
This step is repeated. The average of 10 oscillations is
calculated. Then, the period of oscillation is determined. 4. Steps
2 and 3 are repeated using two and three masses on the inertia
balance. 5. A graph of T2 versus number of masses, n is drawn.
Results: Number of masses, n 1 2 3 Time of oscillations, t (s) t2
Average Period of oscillation, T T = t/10 (s) T2 (s2)
t1
Graph of T2 versus m:
Discussion: The graph of T2 versus m shows a straight line
passing through the origin. This means that the period of
oscillation increases with the mass of the load; that is, an object
with a large mass has a large inertia. Conclusion: Objects with a
large mass have a large inertia. This is the reason why it is
difficult to set an object of large mass in motion or to stop it.
The hypothesis is valid.Chapter 2: Forces and Motion Page 7 of
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2.3 PRINCIPLE OF CONSERVATION OF MOMENTUMExperiment 1: Elastic
collisionsHypothesis: The total momentum before collision is equal
to the total momentum after collision, provided there are no
external forces acting on the system Aim of the experiment: To
demonstrate conservation of momentum for two trolleys colliding
with each other elastically Variables: Manipulated: Mass of
trolleys Responding: Final velocities of the trolleys / Momentum of
the trolleys Constant: Surface of ramp used Apparatus/Materials:
Friction-compensated runway, ticker-timer, A.C. power supply,
trolleys, wooden block, ticker tape, cellophane tape Setup:
Procedure: 1. The apparatus is set up as shown in the diagram.
2. The runway is adjusted so that it is friction-compensated. 3.
Two trolleys of equal mass are selected. A spring-loaded piston is
fixed to the front end of trolley A. 4. Two pieces of ticker tape
are attached to trolleys A and B respectively with cellophane tape.
The ticker tapes are separately passed through the same
ticker-timer. 5. The ticker-timer is switched on and trolley A is
given a slight push so that it moves down the runway at uniform
velocity and collides with trolley B which is stationary. 6. The
ticker-timer is switched off when both trolleys reach the end of
the runway. 7. From the ticker tapes of trolleys A and B, the final
velocities are determined. 8. Momentum is calculated using the
formula p = mv. 9. The experiment is repeated using different
masses of trolleys.
Chapter 2: Forces and Motion
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Recording of data: mA mB Before collision uA Initial total
momentum, mAuA m m 2m m 2m m 2m 2m
vA
vB
After collision Final total momentum, mAvA + mBvB
Analysis: From the above table, it is found that: Total momentum
before collision = Total momentum after collision Conclusion:
Hypothesis proven.
Experiment 2: Inelastic collisionsHypothesis: The total momentum
before collision is equal to the total momentum after collision,
provided there are no external forces acting on the system Aim of
the experiment: To demonstrate conservation of momentum for two
trolleys colliding with each other inelastically Variables:
Manipulated: Mass of trolleys Responding: Final velocities of the
trolleys / Momentum of the trolleys Constant: Surface of ramp used
Apparatus/Materials: Friction-compensated runway, ticker-timer,
A.C. power supply, trolleys, wooden block, ticker tape, cellophane
tape, plasticine / Velcro Setup:
Chapter 2: Forces and Motion
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Procedure: 1. The apparatus is set up as shown in the diagram.
2. The runway is adjusted so that it is friction-compensated. 3.
Two trolleys of equal mass are selected. Plasticine is fixed to the
front end of trolley A. (Alternatively, use Velcro pads) 4. A
ticker tape is attached to trolley A with cellophane tape. The
ticker tape is passed through the ticker-timer. 5. The ticker-timer
is switched on and trolley A is given a slight push so that it
moves down the runway at uniform velocity and collides with trolley
B which is stationary. 6. The ticker-timer is switched off when
both trolleys reach the end of the runway. 7. The final velocity is
determined from the ticker tape. 8. Momentum is calculated using
the formula p = mv. 9. The experiment is repeated using different
masses of trolleys. Results: mA mB u m m 2m 2m m 2m m 2m
Before collision Initial total momentum, mAuA
v
After collision Final total momentum, (mA + mB) v
Analysis: From the above table, it is found that: Total momentum
before collision = Total momentum after collision Conclusion:
Hypothesis proven.
Experiment 3: ExplosionHypothesis: The total momentum before
collision is equal to the total momentum after collision, provided
there are no external forces acting on the system Aim of the
experiment: To demonstrate conservation of momentum for two
trolleys moving away from each other from an initial stationary
position Variables: Manipulated: Mass of trolleys Responding: Final
velocities of the trolleys / Momentum of the trolleys Constant:
Surface used
Chapter 2: Forces and Motion
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Apparatus/Materials: Trolleys, wooden blocks, ticker tape,
cellophane tape Setup:
Before explosion
After explosion
Procedure: 1. The apparatus is set up as shown in the diagram.
2. Two trolleys A and B of equal mass are placed in contact with
each other on an even and smooth surface. Two wooden blocks are
placed on the same row at the end of each trolley respectively. 3.
The vertical trigger on trolley B is given a light tap to release
the spring-loaded piston which then pushes the trolleys apart. The
trolleys collide with the wooden blocks. 4. The positions of the
wooden blocks are adjusted so that both the trolleys collide with
them at the same time. 5. The distances, dA and dB are measured and
recorded. 6. The experiment is repeated with different masses of
trolleys. Results: Before explosion Initial total momentum 0 0 0
0
After explosion Mass of trolley A, mA m m 2m 2m Mass of trolley
B, mB m 2m m 2m Distance traveled by trolley A, dA Distance
traveled by trolley B, dB Final total momentum, mAdA + mB(-dB)
Analysis: Because both trolleys hit the wooden blocks at the
same time, the velocity of the trolleys can be represented by the
distance traveled by the trolleys. From the above table, it is
found that: Initial total momentum = 0 Final total momentum = 0
Total momentum before collision = Total momentum after collision
Conclusion: Hypothesis proven.
Chapter 2: Forces and Motion
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2.4 FORCE, MASS AND ACCELERATIONExperiment 1: Relationship
between acceleration and mass when force is constantHypothesis:
When the force applied is constant, the acceleration of an object
decreases when its mass increases Aim of the experiment: To study
the effect of mass of an object on its acceleration if the applied
force is constant Variables: Manipulated: Mass, m Responding:
Acceleration, a Constant: Applied force, F Apparatus/Materials:
Ticker-timer, A.C. power supply, trolleys, elastic band, runway,
wooden block, ticker tape, cellophane tape Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. A
ticker-tape is attached to the trolley and passed through the
ticker-timer. 3. The ticker-timer is switched on and the trolley is
pulled down the inclined runway with an elastic band attached to
the hind post of the trolley. 4. The elastic band must be stretched
to a fix length that is maintained throughout the motion down the
runway. 5. When the trolley reaches the end of the runway, the
ticker-timer is switched off and the ticker tape is removed. 6.
Starting from a clearly printed dot, the ticker tape is divided
into strips with each strip containing 10 ticks. 7. A ticker tape
chart is constructed, and from the chart, the acceleration of the
trolley is calculated. 8. The experiment is repeated using 2 and 3
trolleys. The elastic band must be stretched to the same fixed
length as in step 4.Chapter 2: Forces and Motion Page 12 of 52
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Results: Mass of trolley, m (kg)1 trolley 2 trolleys 3 trolleys
Analysis: A graph of a against
1 m
Acceleration, a (m s-2)
1 is drawn. m
a
1 mFrom the graph, it shows that a 1 m
Conclusion: The acceleration of an object decreases when the
mass increases. Hypothesis proven.
Experiment 2: Relationship between acceleration and force when
mass is constantHypothesis: When the mass is constant, the
acceleration of an object increases when the applied force
increases Aim of the experiment: To study the effect of force on an
objects acceleration if its mass is constant Variables:
Manipulated: Applied force, F Responding: Acceleration, a Constant:
Mass, m Apparatus/Materials: Ticker-timer, A.C. power supply,
trolleys, elastic band, runway, wooden block, ticker tape,
cellophane tape
Chapter 2: Forces and Motion
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Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. A
ticker-tape is attached to the trolley and passed through the
ticker-timer. 3. The ticker-timer is switched on and the trolley is
pulled down the inclined runway with an elastic band attached to
the hind post of the trolley. 4. The elastic band must be stretched
to a fix length that is maintained throughout the motion down the
runway. 5. When the trolley reaches the end of the runway, the
ticker-timer is switched off and the ticker tape is removed. 6.
Starting from a clearly printed dot, the ticker tape is divided
into strips with each strip containing 10 ticks. 7. A ticker tape
chart is constructed, and from the chart, the acceleration of the
trolley is calculated. 8. The experiment is repeated using 2 and 3
elastic bands. The elastic bands must be stretched to the same
fixed length as in step 4. Results:Force applied, F 1 unit 2 units
3 units Acceleration, a (m s-2)
Analysis: A graph of a against F is drawn. a
F From the graph, it shows that a F Conclusion: The acceleration
of an object increases when the applied force increases. Hypothesis
proven.
Chapter 2: Forces and Motion
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2.5 GRAVITATIONAL ACCELERATIONHypothesis: Gravitational
acceleration does not depend on an objects mass Aim of the
experiment: To measure the acceleration due to gravity Variables:
Manipulated: Mass, m Responding: Gravitational acceleration, g
Apparatus/Materials: Ticker-timer, ticker tape, A.C. power supply,
retort stand, weights (50 g 250 g), G-clamp, cellophane tape, soft
board Setup:
Procedure: 1. Apparatus is setup as shown in the diagram above.
2. One end of the ticker tape is attached to a 50 g weight with
cellophane tape, and the other end is passed through the ticker
timer. 3. The ticker-timer is switched on and the weight is
released so that it falls onto the soft board. 4. The ticker-timer
is switched off when the weight lands on the soft board. 5.
Gravitational acceleration is calculated from the middle portion of
the ticker tape. 6. The experiment is repeated with weights of mass
100 g, 150 g, 200 g, and 250 g.
Chapter 2: Forces and Motion
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Results:Mass of weights (g) 50 100 150 200 250 Free fall
acceleration (m s-2)
Analysis: From the table above, it is found that the
gravitational acceleration for all the weights of different masses
are the same. Discussion: The value of the gravitational
acceleration, g obtained is less than the standard value of 9.81 m
s-2 This is because the weight is not falling freely. It is
affected by: o Air resistance o Friction between ticker tape and
ticker-timer Conclusion Gravitational acceleration is not dependent
on the mass of the object. Hypothesis proven.
2.6 PRINCIPLE OF CONSERVATION OF ENERGYHypothesis: Energy cannot
be created or destroyed, it can only change form. Aim of the
experiment: To investigate the conversion of gravitational
potential energy to kinetic energy. Variables: Manipulated: Mass, m
Responding: Final velocity, v Constant: Height, h
Apparatus/Materials: Ticker-timer, ticker tape, A.C. power supply,
trolley, thread, weights, smooth pulley, friction-compensated
runway, soft board, cellophane tape
Chapter 2: Forces and Motion
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Setup:
Procedure: 1. Apparatus is setup as shown in the diagram above.
2. One end of the ticker tape is attached to the back of the
trolley with cellophane tape and the other end is passed through
the ticker-timer. 3. The ticker-timer is switched on, and the
trolley is released. 4. The final velocity of the trolley and the
weight is determined from the ticker tape obtained. 5. The
experiment is repeated with different masses of trolleys and
weights. Results: Mass of trolley = M kg Mass of weight = m kg
Height of weight before release = h m Final velocity of trolley and
weight = v m s-1 Loss of potential energy of the weight = mgh Final
kinetic energy of the trolley and the weight = (M + m) v2 It is
found that (M + m) v2 = mgh Conclusion The loss of potential energy
is converted to kinetic energy. Hypothesis proven. Note: The
experiment can be modified by making the mass constant and changing
the height of the weights release. Changes must be made to the
variables list and to the last step of the procedure.
Chapter 2: Forces and Motion
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2.7 HOOKES LAWHypothesis: The bigger the weight, the longer the
spring extension Aim of the experiment: To determine the
relationship between the weight and the spring extension Variables:
Manipulated: Weight of the load Responding: Spring extension
Constant: Spring constant Apparatus and Materials: Spring, pin,
weights, plasticine, retort stand, metre rule Setup:
Procedure: 1. The apparatus is setup as shown in the diagram. 2.
The length of the spring without any weights, l0 is measured using
the metre rule with the pin as reference. 3. A 50 g weight is hung
from the bottom of the spring. The new length of the spring, l is
measured. The spring extension is l l0. 4. Step 4 is repeated with
weights 100 g, 150 g, 200 g, and 250 g.
Chapter 2: Forces and Motion
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Results: Original length of spring = l0 = __________ cmLoad mass
(g) 50 g 100 g 150 g 200 g 250 g Load weight (N) 0.5 N 1.0 N 1.5 N
2.0 N 2.5 N Spring length, l (cm) Spring extension, x = l l0
(cm)
Analysis: A graph of spring extension, x against weight, F is
plotted. x
F The x-F graph is a linear graph which passes through the
origin. This shows that the extension of the spring is directly
proportional to the stretching force. Conclusion: Hypothesis
proven.
Chapter 2: Forces and Motion
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CHAPTER 3: FORCES AND PRESSURE3.1 PRESSURE IN LIQUIDSExperiment
1: Water pressure and depthHypothesis: Water pressure increases
with depth Aim of the experiment: To find the relationship between
the pressure in a liquid according to its depth Variables:
Manipulated: Depth of liquid Responding: Pressure in liquid
Constant: Density of liquid Apparatus and Materials: Measuring
cylinder, thistle funnel, rubber tube, manometer, metre rule
Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2.
The measuring cylinder is completely filled with water. 3. The
thistle funnel is lowered into the water to a depth of 10.0 cm. The
manometer reading is measured. The difference in the liquid heights
in the manometer represent the pressure reading. 4. Step 3 is
repeated with values of depth 20.0 cm, 30.0 cm, 40.0 cm and 50.0
cm.
Chapter 3: Forces and Pressure
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Results:Depth (cm) Manometer reading (cm) 10.0 20.0 30.0 40.0
50.0
Analysis: A graph of pressure against depth is drawn.
Pressure
Depth Conclusion: It is observed that the manometer reading
increases as the depth of the thistle funnel increases. This shows
that the pressure increases with the depth of the liquid.
Hypothesis proven.
Experiment 2: Water pressure and densityHypothesis: Pressure in
liquid increases with its density Aim of the experiment: To find
the relationship between the pressure in a liquid and its density
Variables: Manipulated: Density of liquid Responding: Pressure in
liquid Constant: Depth of liquid Apparatus and Materials: Measuring
cylinder, thistle funnel, rubber tube, manometer, metre rule,
water, glycerin, alcohol
Chapter 3: Forces and Pressure
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Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2.
The measuring cylinder is completely filled with water. 3. The
thistle funnel is lowered into the water to a depth of 50.0 cm. The
manometer reading is measured. The difference in the liquid heights
in the manometer represent the pressure reading. 4. The experiment
is repeated by replacing the water with glycerin (density = 1300 kg
m-3) and alcohol (density = 800 kg m-3). Results: Depth within
liquid = 50.0 cmLiquid Density (kg m-3) Manometer reading (cm)
Water 1000 Glycerin 1300 Alcohol 800
Conclusion: It is observed that the manometer reading increases
as the density of the liquid increases. This shows that the
pressure increases with the density of the liquid. Hypothesis
proven.
Chapter 3: Forces and Pressure
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3.2 ARCHIMEDES PRINCIPLEHypothesis: The buoyant force on an
object in a liquid is equal to the weight of the liquid displaced
Aim of the experiment: To find the relationship between the buoyant
force acting upon an object in a liquid and the weight of the
liquid displaced Variables: Manipulated: Weight of the object
Responding: Buoyant force / Weight of liquid displaced Constant:
Density of liquid used Apparatus and Materials: Eureka tin, spring
balance, stone, thread, beaker, triple beam balance Setup:
Procedure: 1. A beaker is weighed with the triple beam balance
and its mass, m1 is recorded. 2. The Eureka tin is filled with
water right up to the level of the overflow hole. The beaker is
placed beneath the spout to catch any water that flows out. 3. A
stone is suspended from the spring balance with thread and its
weight in air, W1 is read from the spring balance.
Chapter 3: Forces and Pressure
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4. The stone is lowered into the Eureka tin until it is
completely immersed in water without touching the bottom of the
Eureka tin. The water will overflow into the beaker. 5. The spring
balance reading, W2 is recorded. 6. The beaker with water is
weighed with the triple beam balance, and the mass, m2 is recorded.
Results: Weight of stone in air = W1 Weight of stone in water = W2
Buoyant force acting on the stone = W2 W1 Weight of the empty
beaker = m1g Weight of the beaker and displaced water = m2g Weight
of the displaced water = (m2 m1)g It is found that W2 W1 = (m2 m1)g
Discussion: The loss of weight of the stone immersed in water is
due to the buoyant force of the water acting upon it. From the
results, it is found that the loss in weight of the stone is equal
to the weight of water displaced. Conclusion: Buoyant force on the
stone = Weight of the water displaced by the stone Hypothesis
proven. Note: Experiment can be modified to compare the weight of
different sized stones and the values of buoyant force
3.3 PASCALS PRINCIPLEHypothesis: The liquid pressure exerted on
a small surface is equal to the liquid pressure exerted on a large
surface in a closed system Aim of the experiment: To find the
relationship between the pressure in a small syringe and a large
syringe in a closed system Variables: Manipulated: Pressure acting
on the small syringe Responding: Pressure acting on the large
syringe Constant: Density of liquid within the system
Chapter 3: Forces and Pressure
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Apparatus and Materials: 5 ml syringe, 10 ml syringe, several
weights, rubber tube, two retort stands Setup:
Procedure: 1. The diameters of the piston of both syringes are
measured and their cross-sectional areas are calculated. 2. The two
syringes are each mounted on a retort stand. 3. The syringes are
filled with water and are securely connected to each other with a
rubber tube as shown in the diagram. 4. A weight is placed on the
piston of the small syringe. 5. Weights are added to the piston of
the large syringe until the water levels in the two syringes are
the same (i.e. syringes are in equilibrium). 6. The forces, F1 and
F2 on the syringes are calculated. 7. The pressure, P1 and P2
exerted on the syringes are compared. Results: Syringe size Small
LargePressure, P F = A P1 P2
Cross-sectional area, A
Mass of the weight, m
Force exerted on the syringe, F = mg
A1 A2
m1 m2
F1 F2
Discussion: It is found that the pressure, P1 exerted on the
piston of the small syringe is equal to the pressure, P2 exerted on
the piston of the large syringe. Conclusion: The water pressure
exerted on the piston of the small syringe is equal to the water
pressure exerted on the piston of the large syringe. This shows
that the pressure applied to the piston of the small syringe is
transmitted to the piston of the large syringe. Hypothesis
proven.
Chapter 3: Forces and Pressure
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3.4 BERNOULLIS PRINCIPLEHypothesis: When the velocity of water
increases, its pressure decreases and vice versa. Aim of the
experiment: To find the effects of movement on the pressure exerted
by a fluid Variables: Manipulated: Velocity of the water
Responding: Pressure of the water Constant: Density of the water
Apparatus and Materials: Uniform glass tube, Venturi tube, rubber
hose, water from a tap Procedure: 1. A uniform glass tube is
connected to a tap with a rubber hose. The other end of the tube is
closed up with a stopper. 2. The tap is opened slowly so that water
flows into it. 3. The levels of the vertical tubes are observed. 4.
The stopper is then removed. The tap is adjusted so that the water
flows through the tube at a uniform rate. 5. The levels of the
vertical tubes are observed. 6. The experiment is repeated by
replacing the uniform glass tube with a Venturi tube. Results:
Uniform glass tube:
With the stopper
Without the stopper
Chapter 3: Forces and Pressure
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Venturi tube:
With the stopper
Without the stopper
Discussion: The height of the water in the vertical tube
represents the pressure at that point. When water is not flowing,
the pressure along the entire tube is the same, therefore the water
levels in all three vertical tubes are the same. For the uniform
glass tube: o Water flows from high pressure to low pressure. o
Therefore, the water levels are decreasing because the pressure is
decreasing. For the Venturi tube: o The velocity at Y is higher
because of the smaller cross-sectional area. o Therefore, the
pressure at Y is the lowest. o Pressure still decreases from X to Z
because water flows from high pressure to low pressure. Conclusion:
The higher the water velocity, the lower the pressure at that
point. Hypothesis proven.
Chapter 3: Forces and Pressure
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CHAPTER 4: HEAT AND ENERGY4.1 SPECIFIC HEAT CAPACITYExperiment
1: Rise in temperature varying mass, fixed amount of
heatHypothesis: The bigger the mass of water, the smaller the rise
in temperature when supplied with the same amount of heat Aim of
the experiment: To determine the rise in temperature of water with
varying masses Variables: Manipulated: Mass of water, m Responding:
Rise in temperature, Constant: Amount of heat supplied, Q Apparatus
and Materials: Beaker, electric heater, thermometer, stopwatch,
triple beam balance, stirrer, polystyrene sheet, felt cloth Set
up:
Procedure: 1. With the help of a triple beam balance, fill a
beaker with water of mass 0.40 kg. 2. The apparatus is set up as
shown in the diagram. 3. The initial temperature of the water, 1 is
measured using a thermometer and is recorded. 4. The electric
heater is placed into the water and is switched on for 1 minute.
The water is continuously stirred. 5. The water is continuously
stirred even after the heater has been switched off. The
Chapter 4: Heat and Energy
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6. The highest temperature the water reaches, 2 is measured and
recorded. The rise in temperature, = 2 1 is calculated. 7. The
experiment is repeated with water of mass 0.50 kg, 0.60 kg, 0.70
kg, and 0.80 kg. 1 8. A graph of against m and a graph of against
are plotted. m Results: Mass of water, Initial Final Rise in 1
(kg-1) m (kg) temperature, temperature, temperature, m 1 (C) 2 (C)
= 2 1 (C)0.40 0.50 0.60 0.70 0.80
Analysis: The amount of heat supplied is made constant by using
the same heater for the same period of time. The following graphs
are obtained:
Conclusion: The rise in temperature is inversely proportional to
the mass when a constant amount of heat is supplied. Hypothesis
proven.
Experiment 2: Rise in temperature fixed mass, varying amount of
heatHypothesis: When more heat is supplied to water of fixed mass,
the rise in temperature is greater Aim of the experiment: To
determine the rise in temperature of water with varying amounts of
heat Variables: Manipulated: Amount of heat supplied, Q Responding:
Rise in temperature, Constant: Mass of water, m
Chapter 4: Heat and Energy
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Apparatus and Materials: Beaker, electric heater, thermometer,
stopwatch, triple beam balance, stirrer, polystyrene sheet, felt
cloth Set up:
Procedure: 1. With the help of a triple beam balance, fill a
beaker with water of mass 0.50 kg. 2. The apparatus is set up as
shown in the diagram. 3. The initial temperature of the water, 1 is
measured using a thermometer and is recorded. 4. The electric
heater is placed into the water and is switched on for 1 minute.
The water is continuously stirred. 5. The water is continuously
stirred even after the heater has been switched off. 6. The highest
temperature the water reaches, 2 is measured and recorded. The rise
in temperature, = 2 1 is calculated. 7. The experiment is repeated
with water of the same mass but with heating time of 2 minutes, 3
minutes, and 4 minutes. 8. A graph of against t is plotted.
Results:Heating time (minute) Initial temperature, 1 (C) Final
temperature, 2 (C) Rise in temperature, = 2 1 (C)
1 2 3 4 Analysis: Because the same heater with fixed power is
used, the heating time, t is defined operationally as the heat
quantity. The following graph is obtained:
Chapter 4: Heat and Energy
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Conclusion: When an object of fixed mass is heated, the rise in
temperature changes proportionally to the amount of heat supplied.
Hypothesis proven.
Experiment 3: Determining the specific heat capacity of
aluminiumAim of the experiment: To determine the specific heat
capacity of aluminium Apparatus and Materials: Aluminium cylinder,
weighing scale, electric heater, thermometer, power supply, felt
cloth, polystyrene sheet, stopwatch, lubricating oil Set up:
Procedure: 1. An aluminium cylinder with two cavities is weighed
and its mass, m is recorded. 2. The electrical power of the heater,
P is recorded. 3. The electrical heater is then placed inside the
large cavity in the centre of the cylinder. 4. The thermometer is
then placed in the small cavity of the aluminium cylinder. 5. A few
drops of lubricating oil are added to both cavities to ensure good
thermal contact (better heat transfer). 6. The apparatus is set up
as shown in the diagram above. 7. The initial temperature of the
aluminium cylinder, 1 is recorded. 8. The electric heater is
switched on and the stopwatch is started simultaneously. 9. After
heating for t seconds, the heater is switched off. The highest
reading on the thermometer, 2 is recorded. 10. The experiment is
repeated and an average value of c is calculated.
Chapter 4: Heat and Energy
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Results: Electric power of heater = P Watt Heating time = t
seconds Mass of aluminium cylinder = m kg Initial temperature of
the aluminium cylinder = 1 Final temperature of the aluminium
cylinder = 2 Temperature rise = 2 1 Electrical energy supplied by
the heater = Pt Heat energy absorbed by the aluminium cylinder = mc
On the assumption that there is no heat loss to the surroundings:
Heat supplied = Heat absorbed Pt = mc Pt Specific heat capacity, c
= m Discussion: The aluminium cylinder is wrapped with a felt cloth
to reduce the heat loss to the surroundings and the polystyrene
sheet acts as a heat insulator to avoid heat loss to the surface of
the table. The value of the specific heat capacity of aluminium, c
determined in the experiment is larger than the standard value.
This is because there will be some heat lost to the surrounding.
The temperature of the aluminium cylinder will continue to rise
after the electrical heater has been switched off because there is
still some heat transfer from the heater to the cylinder.
Conclusion: The specific heat capacity of aluminium is a
constant.
4.2 SPECIFIC LATENT HEATExperiment 1: Heating of
naphthaleneHypothesis: During the change of state of naphthalene
from solid to liquid, there is no change in temperature when heat
is continuously supplied Aim of the experiment: To observe the
change in temperature when naphthalene is melting Apparatus and
Materials: Boiling tube, naphthalene powder, beaker, thermometer,
Bunsen burner, stopwatch, retort stand, tripod stand, wire
gauzeChapter 4: Heat and Energy Page 32 of 52
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Set up:
Procedure: 1. The apparatus is set up as shown in the diagram.
2. The initial temperature of the naphthalene is recorded. 3. The
Bunsen burner is lighted and the stopwatch started. 4. The
temperature of the naphthalene is recorded at 1 minute intervals
until the temperature reaches 100C. 5. The state of the naphthalene
is observed and tabulated throughout the heating process. 6. A
graph of temperature against time is drawn. Results:Time, t
(minute) Temperature of naphthalene, (C) 0 1 2 3
Graph of temperature against time:
Discussion: The temperature-time graph shows that the
temperature of naphthalene rises until the naphthalene starts to
melt. The naphthalene starts to melt at 80C. The temperature
remains constant at this value for several minutes while the
naphthalene continues to melt with the heat.
Chapter 4: Heat and Energy
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After the naphthalene has completely melted, the temperature
begins to rise with continued heating.
Conclusion: The temperature of the naphthalene remains constant
during a change of state from solid to liquid.
Experiment 2: Cooling of naphthaleneHypothesis: During the
change of state of naphthalene from liquid to solid, there is no
change in temperature Aim of the experiment: To observe the change
in temperature when naphthalene is freezing Apparatus and
Materials: Boiling tube, naphthalene powder, beaker, thermometer,
Bunsen burner, stopwatch, retort stand, tripod stand, wire gauze
Set up:
Procedure: 1. The apparatus is set up as shown in the diagram.
2. The naphthalene is heated until the temperature reaches 95C. 3.
The boiling tube is then removed from the water bath and the outer
part of the tube is dried. 4. The temperature of the naphthalene is
recorded every minute until the temperature drops to about 60C. 5.
A graph of temperature against time is drawn.
Chapter 4: Heat and Energy
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Results:Time, t (minute) Temperature of naphthalene, (C) 0 1 2
3
Graph of temperature against time:
Discussion: The temperature-time graph shows that the
temperature of naphthalene drops until 80C where it stays constant
for several minutes as it freezes. After the naphthalene has
completely frozen, the temperature continues to drop. Conclusion:
The temperature of the naphthalene remains constant during a change
of state from liquid to solid.
Experiment 3: Latent heat of fusion (ice)Aim of the experiment:
To determine the latent heat of fusion of ice Apparatus and
Materials: Pure ice, electric immersion heater, filter funnel,
beaker, stopwatch, weighing balance, power supply, retort stand,
clamp
Chapter 4: Heat and Energy
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Set up:
Set A
Set B
Procedure: 1. The mass of two empty beakers, A and B are
determined using the weighing balance. 2. The apparatus is arranged
as shown in the diagram above. 3. Each of the two filter funnels is
filled with ice cubes. 4. The immersion heater in Set A, the
control experiment, is not connected to the power supply. The
purpose of Set A is to determine the mass of the ice melted by the
surrounding heat. The heater in Set B is switched on. 5. When water
starts to drip from the filter funnels at a steady rate, the
stopwatch is started and the empty beakers A and B are placed
beneath the filter funnels. 6. After a period of t seconds, the
heater B is switched off. The masses of both beakers, A and B are
determined using the weighing balance. 7. The experiment is
repeated to get an average value. Results: Set A: Mass of empty
beaker = mA1 kg Mass of beaker + water = mA2 kg Mass of ice melted
by surrounding heat, ma = mA2 mA1 kg Set B: Mass of empty beaker =
mB1 kg Mass of beaker + water = mB2 kg Mass of ice melted by
surrounding heat & immersion heater, mb = mB2 mB1 kg Mass of
ice melted by the electric immersion heater, m = mb ma kg
Electrical energy supplied by the electrical immersion heater, E =
Pt Heat energy absorbed by the ice during melting, Q = mL Assuming
there is no heat loss to the surroundings: Electrical energy
supplied = Heat energy absorbed by the melting ice Pt = mL Pt
Specific latent heat of fusion of ice, L = mChapter 4: Heat and
Energy Page 36 of 52
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Discussion: The purpose of Set A, the control experiment, is to
determine the mass of ice melted by the surrounding heat. The
immersion heater must be fully immersed in the ice cubes to avoid
or reduce heat loss. The stopwatch is not started simultaneously
when the immersion heater is switched on because the immersion
heater requires a time period before reaching a steady temperature.
At this point, the rate of melting of ice will be steady. The value
of the specific latent heat of fusion of ice, L obtained in this
experiment is higher than the standard value because part of the
heat supplied by the heater is lost to the surroundings.
Conclusion: The specific latent heat of fusion of ice is a
constant.
Experiment 4: Latent heat of vapourisation (water)Aim of the
experiment: To determine the latent heat of vapourisation of water
Apparatus and Materials: Pure water, electric immersion heater,
filter funnel, beaker, stopwatch, weighing balance, power supply,
retort stand, clamp Set up:
Procedure: 1. The apparatus is set up as shown in the diagram
above. 2. A beaker is placed on the platform of the electronic
weighing balance. 3. The electric heater is fully immersed in the
water and held in this position by being clamped to a retort stand.
4. The electric heater is switched on to heat the water to its
boiling point. 5. When the water starts to boil at a steady rate,
the stopwatch is started and the reading on the electronic balance,
m1 is recorded. 6. The water is allowed to boil for a period of t
seconds. 7. At the end of the period of t seconds, the reading on
the electronic balance, m2 is recorded.
Chapter 4: Heat and Energy
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Results: Electrical power of heater = P Watt Time period of
boiling = t seconds Electrical energy supplied by the electrical
immersion heater, E = Pt Mass of water vapourised = m2 m1 Heat
energy absorbed by the water during vapourisation, Q = mL Assuming
there is no heat loss to the surroundings: Electrical energy
supplied = Heat energy absorbed by the vapourized water Pt = mL Pt
Specific latent heat of vapourization of water, L = m Discussion:
The immersion heater must be fully immersed in the water to avoid
or reduce heat loss. The stopwatch is not started simultaneously
when the immersion heater is switched on because the immersion
heater requires a time period before reaching a steady temperature.
At this point, the rate of heating of water will be steady. The
value of the specific latent heat of vapourization of water, L
obtained in this experiment is higher than the standard value
because part of the heat supplied by the heater is lost to the
surroundings. Conclusion: The specific latent heat of vapourization
of water is a constant.
4.3 BOYLES LAWOption 1: Changing the volume of air to measure
pressureHypothesis: When the volume of air decreases, the pressure
increases when its mass and temperature is constant Aim: To
investigate the relationship between the pressure and volume of air
Variables: Manipulated: Volume of air within syringe Responding:
Pressure of air Constant: Mass, temperature of air Apparatus and
Materials: Rubber hose, Bordon gauge, 100 cm3 syringeChapter 4:
Heat and Energy Page 38 of 52
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Set up:
Procedure: 1. Apparatus is set up as per the diagram. 2. The
nose of the syringe is fitted with a rubber hose and the piston is
adjusted so that air volume of 100 cm3 at atmospheric pressure is
trapped in the syringe. 3. The rubber hose is connected to a
Bourdon gauge and air pressure is read from the gauge. 4. The
piston of the syringe is pushed in until the trapped air volume
becomes 90 cm3 and the air pressure is read from the Bourdon gauge.
5. Step 4 is repeated for air volume values 80, 70, and 60 cm3.
Results:Volume, V (cm3)
1 (cm-3) V
Pressure, P (Pa)
100 90 80 70 60 Analysis:
1 is plotted. V A linear graph going through the origin is
obtained. This indicates that pressure is inversely proportional to
the volume of gas. A graph of P against
Conclusion: Gas pressure of fixed mass is inversely proportional
to its volume.
Chapter 4: Heat and Energy
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Option 2: Changing the pressure of air to measure
volumeHypothesis: When the pressure of air decreases, the volume
increases when its mass and temperature is constant Aim: To
investigate the relationship between the pressure and volume of air
Variables: Manipulated: Pressure of air Responding: Volume of air
trapped in the capillary tube Constant: Mass, temperature of air
Apparatus and Materials: Bicycle pump, ruler, tank with oil,
pressure gauge, glass tube Set up:
Procedure: 1. The apparatus is set up as shown in the diagram
above. 2. The piston of the bicycle pump is pushed in to compress
the air inside the glass tube until the pressure is 10 kPa. 3. When
the reading on the pressure gauge is P, the volume of the air
column, V is recorded. 4. Steps 1 and 2 are repeated for 5 pressure
readings of 20 kPa, 30 kPa and 40 kPa.
Chapter 4: Heat and Energy
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Results: Pressure, P (kPa) 10 20 30 40 Analysis:
1 (Pa-1) P
Volume, V (cm3)
1 is plotted. P A linear graph going through the origin is
obtained. This indicates that pressure is inversely proportional to
the volume of gas.A graph of V against
Conclusion: Volume of gas of fixed mass is inversely
proportional to its pressure.
4.4 CHARLES LAWHypothesis: When the temperature of air
increases, the volume increases if the mass and pressure is
constant Aim: To investigate the relationship between the volume
and the temperature of gas Variables: Manipulated: Air temperature
Responding: Air volume Constant: Mass and pressure of the trapped
air Apparatus and Materials: Capillary tube, tall beaker,
thermometer, Bunsen burner, tripod, wire gauze, retort stand,
mercury or concentrated sulphuric acid, stirrer, ruler, ice, rubber
band
Chapter 4: Heat and Energy
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Set up:
Procedure: 1. Apparatus is set up as per the diagram. 2. The air
to be studied is trapped in a capillary tube by concentrated
sulphuric acid. 3. The capillary tube is fitted to a ruler using
two rubber bands and the bottom end of the air column is ensured to
match the zero marking on the ruler. 4. Water and ice is poured
into the beaker until the whole air column is submerged. Water is
then stirred until the temperature rises to 10 C. The length of the
air column and the temperature of the water are recorded. 5. Water
is heated slowly while being stirred continuously. The length of
the air column is recorded every 10 C until the water temperature
reaches 90 C. Results: 10 20 30 40 50 60 70 80 90 Temperature, (C)
Length of air column, x (cm) Analysis: A graph of x against is
plotted. A linear graph is obtained. When extrapolated, length x =
0 occurs when gas temperature, = -273 C
When the Celsius scale is replaced with the Kelvin scale, a
linear graph that goes through origin is obtained.
Chapter 4: Heat and Energy
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Discussion: From the graph plotted, it is found that the length
of the air column, x is directly proportional to its temperature, T
(K). Because gas volume is directly proportional to the length of
the column, it also indicates that gas volume is directly
proportional to its absolute temperature. Conclusion: Gas volume of
fixed mass is directly proportional to its absolute temperature
4.5 PRESSURE LAWHypothesis: When the temperature of air
increases, the pressure increases if the mass and volume is
constant Aim: To investigate the relationship between the pressure
and the temperature of gas Variables: Manipulated: Air temperature
Responding: Air pressure Constant: Mass and volume of the trapped
air Apparatus and Materials: Round-bottomed flask, mercury
thermometer, Bourdon gauge, Bunsen burner, tripod, wire gauze,
retort stand, stirrer, ice Set up:
Chapter 4: Heat and Energy
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Procedure: 1. Apparatus is set up as per the diagram. 2. The
round-bottomed flask is submerged in water and the water bath with
ice is stirred continuously until the temperature of the water bath
is stable. 3. The temperature of the water is taken from the
thermometer. 4. The reading from the Bourdon gauge is read at
temperatures 30, 40, 50, 60, 70 and 80 C. Results: Temperature, (C)
30 40 50 60 70 80 Air pressure, P (Pa) Analysis: A graph of P
against is plotted. A linear graph is obtained. When extrapolated,
pressure P = 0 occurs when gas temperature, = -273 C
When the Celsius scale is replaced with the Kelvin scale, a
linear graph that goes through origin is obtained.
Conclusion: Gas pressure of fixed mass is directly proportional
to its absolute temperature
Chapter 4: Heat and Energy
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CHAPTER 5: LIGHT AND VISION5.1 REFLECTIONHypothesis: The angle
of reflection is equal to the angle of incidence Aim of the
experiment: To study the relationship between the angle of
incidence and angle of reflection Variables: Manipulated: Angle of
incidence, i Responding: Angle of reflection, r Constant: Plane
mirror used Apparatus/Materials: Light box, plane mirror,
plasticine, paper, pencil, protractor Setup:
Procedure: 9. A straight line, PQ is drawn on a sheet of white
paper. 10. The normal line, ON is drawn from a point at the centre
of PQ. 11. With the aid of a protractor, lines at angles of
incidence 15, 30, 45, 60 and 75 to the normal line, are drawn to
its left. 12. A plane mirror is erected along the line PQ. It is
secured in this position with the aid of plasticine. 13. A ray of
light from the ray box is directed along the 15 line. Two positions
are marked with a pencil on the line of the reflected ray. 14. Step
5 is repeated for the other angles of incidence. 15. The plane
mirror is removed. The reflected rays are drawn by joining the
respective marks. 16. The angles of reflection corresponding with
all the angle of incidence are measured. The results are
tabulated.
Chapter 5: Light and Vision
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Results:Incident angle () Reflected angle () 15 30 45 60 75
Conclusion: The angle of incidence is equal to the angle of
reflection.
5.2 CURVED MIRRORSAim of the experiment: To study the
characteristics of images formed by curved mirrors
Apparatus/Materials: Concave mirror, convex mirror, plasticine,
light bulb mounted on a wooden block, metre rule, white screen
Setup:
Procedure: 1. The apparatus is set up as shown in the diagram.
2. The focal length, f and the radius of curvature, r of the
concave mirror, as supplied, are recorded. 3. The light bulb is
positioned at a distance greater than the radius of curvature of
the mirror, i.e. u > 2f. The white screen is moved between the
concave mirror and the light bulb until an image is clearly focused
on the screen. The image distance, v is measured by a metre rule
and recorded. 4. Step 3 is repeated with the light bulb positioned
at C (u = 2f), between C and F (f < u < 2f), at F (u = f),
and between F and P (u < f).
Chapter 5: Light and Vision
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5. The values of u, v, and the characteristics of the images
formed are recorded in a table. 6. The experiment is repeated by
replacing the concave mirror with a convex mirror. Results: Concave
mirror; Position of Object object distance, u (cm) Beyond C (u >
2 f ) At C (u = 2 f ) Between C and F (f < u < 2f) At F (u =
f) Between F and P (u < 2 f ) Convex mirrors: For all positions,
the image characteristics are: __________________________
Conclusion: For concave mirrors, images formed can be real or
virtual, whereas for convex mirrors, only virtual images are
formed. The characteristics of images formed by the concave mirror
depend on the position of the object.
Image distance, v (cm)
Characteristics of image Real / Upright / Diminished / Virtual
Inverted Magnified / Same size
5.3 REFRACTIONHypothesis:The refracted light ray obeys Snells
Law which states that the value of constant where i is the angle of
incidence and r is the angle of refraction
sin i is a sin r
Aim of the experiment: To study the relationship between the
angle of incidence and angle of refraction
Chapter 5: Light and Vision
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Variables: Manipulated: Angle of incidence, i Responding: Angle
of refraction, r Constant: Plane mirror used Apparatus/Materials:
Ray box, glass block, paper, pencil Setup:
Procedure: 1. The outline of the glass block is traced on a
sheet of white paper and labeled. 2. The glass block is removed.
Point O is marked on one side of the glass block. With a
protractor, lines forming angles of incidence 20, 30, 40, 50 and 60
are drawn and marked. 3. The glass block is replaced on its outline
on the paper. 4. A ray of light from the ray box is directed along
20 line. The ray emerging on the other side of the block is drawn.
5. Step 4 is repeated for the other angles of incidence. 6. The
glass slab is removed. The points of incidence and the
corresponding points of emergence are joined. The respective angles
of refraction are measured with a protractor. sin i 7. The values
of sin i, sin r, and are calculated. sin r Results: Angle of
incidence, i () Angle of refraction, r () Sin i Sin r 20 30 40 50
60 Conclusion: It is found that
n=
sin i sin r
sin i is a constant. Hypothesis valid. sin r
Chapter 5: Light and Vision
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5.4 ACTUAL DEPTH & APPARENT DEPTHHypothesis: The deeper the
actual depth, the deeper the apparent depth Aim of the experiment:
To study the relationship between the actual depth and apparent
depth Variables: Manipulated: Actual depth, D Responding: Apparent
depth, d Constant: Refractive index of medium (water), n
Apparatus/Materials: Tall beaker, 2 pins, ruler, metre rule, retort
stand Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. A
pin is mounted on a movable clamp on a retort stand. 3. Another pin
is placed at the base of the tall beaker. Water is filled as the
actual depth to D = 7.0 cm. 4. The object pin O is observed from
the top, and pin I is adjusted vertically until it appears to meet
pin O. At this point, the position of pin I matches the apparent
depth, d of pin O. The apparent depth is measured from the top of
the water level to the position of pin I. 5. Step 4 is repeated by
changing the actual depth to 9.0 cm, 11.0 cm, 13.0 cm and 15.0 cm.
6. The results are tabulated and a graph of D against d is
plotted.
Chapter 5: Light and Vision
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Results:Actual depth, D (cm) Apparent depth, d (cm) 7.0 9.0 11.0
13.0 15.0
Analysis: A linear graph that goes through origin is obtained.
D
d Discussion: The gradient of the graph is equal to the index of
refraction of water. Conclusion: Hypothesis is valid
5.5 TOTAL INTERNAL REFLECTIONAim of the experiment: To determine
the critical angle of glass Apparatus/Materials: Semicircular glass
block, ray box, protractor, white paper, pencil Setup:
Procedure: 1. A semicircular glass block is placed on a sheet of
white paper. The outline of the glass block is traced onto the
paper with a sharp pencil.Chapter 5: Light and Vision Page 50 of
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2. The glass block is put aside. A normal line, NN is drawn
through the centre point, O on the diameter. 3. The glass block is
replaced on its outline. 4. A narrow beam of light from the ray box
is directed at point O at a small angle of incidence. The refracted
and reflected rays are observed. 5. The angle of incidence, i
measured from the normal line is adjusted until the light ray is
refracted along the length of the air-glass boundary. The point of
entry of the light ray is marked and measured with a protractor. At
this point, the incident angle is known as the critical angle, c.
6. The angle of incidence is increased and the resultant rays are
observed. 7. The experiment is repeated by pointing the light ray
through the other side of the semicircle. Results: When i < c,
part of the light ray is refracted to the air, and part of it will
be reflected back within the glass block When i = c, the light ray
will be refracted along the length of the glass-air boundary When i
> c, no refraction occurs; all the light ray will be totally
internally reflected within the glass block Analysis: The critical
angle, c is a constant. 1 Refractive index of glass, n = sin c
Conclusion: The refractive index of glass, n = 1 sin c
5.6 LENSESHypothesis: The image produced by a convex lens is
virtual or real depending on the position of the object. The
characteristics of an image produced by a concave lens is not
affected by the object distance. Variables: Manipulated: Object
distance, u Responding: Image distance, v Constant: Focal length of
lens, f Apparatus/Materials: Cardboard with a cross-wire in
triangular cut-out, light bulb, lens holder, convex lens, concave
lens, white screen
Chapter 5: Light and Vision
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Setup:
Procedure: 1. The apparatus is set up as shown in the diagram.
2. The focal length, f of the convex lens supplied is recorded. 3.
The object (triangle with a cross-wire) is placed at a distance
greater than 2f from the convex lens. 4. The white screen is moved
back and forth until a sharp image of the triangle is formed on the
screen. The image distance, v is measured. The characteristics of
the image are observed and recorded in a table. 5. Step 3 is
repeated wit the object distances, u = 2f, f < u < 2f, u = f,
and u < f. 6. For positions where the image cannot be formed on
the screen, the screen is removed and the image is viewed through
the lens from the other side of the lens. 7. The experiment is
repeated by replacing the convex lens with a concave lens. Results:
Convex lens: Position Object of object distance, u (cm) u > 2f u
= 2f f < u < 2f u=f u < 2f Concave lens: For all
positions, the image characteristics are:
__________________________ Conclusion: For convex lenses, images
formed can be real or virtual, whereas for concave lenses, only
virtual images are formed. The characteristics of images formed by
the convex lens depend on the position of the object.
Image distance, v (cm)
Characteristics of image Real / Upright / Diminished / Virtual
Inverted Magnified / Same size
Chapter 5: Light and Vision
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