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CHAPTER 1:INTRODUCTION TO PHYSICS1.1 PENDULUM
Hypothesis: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,
lResponding: The period of the pendulum, TConstant: The mass of the
pendulum bob, gravitational
accelerationApparatus/Materials:Pendulum bob, length of thread
about 100 cm long, retort stand, stopwatchSetup:Length, l
Thread
Retort standPendulumProcedure: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 1 of 522. 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 thestopwatch.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)Time of oscillations, t (s)Period of oscillation,
T
t1t2AverageT = t/10 (s)T2 (s2)
80
70
60
50
40
Graph of T2 vs lT2Length of pendulum, lDiscussion: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 Page 2 of 52
CHAPTER 2:FORCES AND MOTION2.1 INCLINED PLANES
Hypothesis:The larger the angle of incline, the higher the
velocity just before reaching the end of the runwayAim of the
experiment:To study the relationship between the velocity of motion
and the angle of inclinationVariables:Manipulated: Angle of
inclineResponding: Velocity just before reaching the end of the
runwayConstant: Length of runwayApparatus/Materials: Trolley,
protractor, wooden blocks, cellophane tape, ticker- timer, ticker
tape, power supply, friction-compensated runwaySetup:
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 downthe 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 Page 3 of 52Results: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 Page 4 of 522.2 INERTIA
Option 1: Using a saw bladeHypothesis:The larger the mass, the
larger the inertiaAim of the experiment:To study the effect of mass
on the inertia of an objectVariables: Manipulated: Mass,
mResponding: Period of oscillation, TConstant: Stiffness of blade,
distance of the centre of the plasticine from the
clampApparatus/Materials: Jigsaw blade, G-clamp, stopwatch, and
plasticine spheres of mass 20 g, 40 g, 60 g, 80 g, and 100
gSetup: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 Page 5 of 52Results:Mass of
load, m (g)Time of oscillations, t (s)Period of oscillation, T
t1t2AverageT = t/10 (s)T2 (s2)
20
40
60
80
100
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 inertiaAim of
the experiment:To study the effect of mass on the inertia of an
objectVariables: Manipulated: Mass, mResponding: Period of
oscillation, TConstant: Stiffness of the inertia
balanceApparatus/Materials: Inertia balance, masses for the inertia
balance, G-clamp, stopwatchChapter 2: Forces and Motion Page 6 of
52Setup: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, nTime of oscillations, t (s)Period
of oscillation, T
t1t2AverageT = t/10 (s)T2 (s2)
1
2
3
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
522.3 PRINCIPLE OF CONSERVATION OF MOMENTUM
Experiment 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 systemAim of
the experiment:To demonstrate conservation of momentum for two
trolleys colliding with each other
elasticallyVariables:Manipulated: Mass of trolleysResponding: Final
velocities of the trolleys / Momentum of the trolleysConstant:
Surface of ramp usedApparatus/Materials: Friction-compensated
runway, ticker-timer, A.C. power supply, trolleys, wooden block,
ticker tape, cellophane tapeSetup: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
withcellophane 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
Page 8 of 52Recording of data:mAmBBefore collisionAfter
collision
uAInitial total momentum,mAuAvAvBFinal total momentum,mAvA +
mBvB
mm
m2m
2 mm
2 m2 m
Analysis:From the above table, it is found that:Total momentum
before collision = Total momentum after collisionConclusion:
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 systemAim of the experiment:To demonstrate conservation of
momentum for two trolleys colliding with each other
inelasticallyVariables:Manipulated: Mass of trolleysResponding:
Final velocities of the trolleys / Momentum of the
trolleysConstant: Surface of ramp usedApparatus/Materials:
Friction-compensated runway, ticker-timer, A.C. power supply,
trolleys, wooden block, ticker tape, cellophane tape, plasticine /
VelcroSetup:Chapter 2: Forces and Motion Page 9 of 52Procedure: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
trolleyA. (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:mAmBBefore collisionAfter collision
uInitial total momentum,mAuAvFinal total momentum, (mA + mB)
v
mm
m2m
2 mm
2 m2 m
Analysis:From the above table, it is found that:Total momentum
before collision = Total momentum after collisionConclusion:
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
systemAim of the experiment:To demonstrate conservation of momentum
for two trolleys moving away from each other from an initial
stationary positionVariables:Manipulated: Mass of
trolleysResponding: Final velocities of the trolleys / Momentum of
the trolleysConstant: Surface usedChapter 2: Forces and Motion Page
10 of 52
Apparatus/Materials: Trolleys, wooden blocks, ticker tape,
cellophane tapeSetup:Before explosion After explosionProcedure: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 explosionAfter explosion
Initial total momentumMass of trolley A, mAMass of trolley B,
mBDistance traveled by trolley A, dADistance traveled by trolley B,
dBFinal total momentum, mAdA + mB(-dB)
0mm
0m2m
02 mm
02m2m
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 = 0Final total momentum = 0 Total
momentum before collision = Total momentum after
collisionConclusion: Hypothesis proven.Chapter 2: Forces and Motion
Page 11 of 522.4 FORCE, MASS AND ACCELERATION
Experiment 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 increasesAim of
the experiment:To study the effect of mass of an object on its
acceleration if the applied force is constantVariables:
Manipulated: Mass, m Responding: Acceleration, a Constant: Applied
force, FApparatus/Materials: Ticker-timer, A.C. power supply,
trolleys, elastic band, runway, wooden block, ticker tape,
cellophane tapeSetup: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 andthe 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 iscalculated.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
52Results:Mass of trolley, m (kg)1mAcceleration, a (m s-2)
1 trolley
2 trolleys
3 trolleys
Analysis:A graph of a againsta
1 is drawn.m1mFrom the graph, it shows that a 1mConclusion: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 increasesAim of the experiment:To study the effect of force
on an objects acceleration if its mass is
constantVariables:Manipulated: Applied force, F Responding:
Acceleration, a Constant: Mass, mApparatus/Materials: Ticker-timer,
A.C. power supply, trolleys, elastic band, runway, wooden block,
ticker tape, cellophane tapeChapter 2: Forces and Motion Page 13 of
52Setup: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 themotion 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 iscalculated.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, FAcceleration, a
(m s-2)
1 unit
2 units
3 units
Analysis:A graph of a against F is drawn.aFFrom the graph, it
shows that a FConclusion:The acceleration of an object increases
when the applied force increases. Hypothesis proven.
Chapter 2: Forces and Motion Page 14 of 522.5 GRAVITATIONAL
ACCELERATION
Hypothesis:Gravitational acceleration does not depend on an
objects massAim of the experiment:To measure the acceleration due
to gravityVariables: Manipulated: Mass, mResponding: Gravitational
acceleration, gApparatus/Materials: Ticker-timer, ticker tape, A.C.
power supply, retort stand, weights (50 g 250 g), G-clamp,
cellophane tape, soft boardSetup: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
softboard.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 Page 15 of 52Results:Mass of weights (g)Free fall
acceleration (m s-2)
50
100
150
200
250
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 valueof 9.81 m
s-2 This is because the weight is not falling freely. It is
affected by:o Air resistanceo Friction between ticker tape and
ticker-timerConclusionGravitational acceleration is not dependent
on the mass of the object. Hypothesis proven.2.6 PRINCIPLE OF
CONSERVATION OF ENERGY
Hypothesis: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, hApparatus/Materials: Ticker-timer, ticker tape, A.C. power
supply, trolley, thread, weights, smooth pulley,
friction-compensated runway, soft board, cellophane tapeChapter 2:
Forces and Motion Page 16 of 52
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 kgMass of weight = m
kgHeight of weight before release = h mFinal velocity of trolley
and weight = v m s-1Loss of potential energy of the weight =
mghFinal kinetic energy of the trolley and the weight = (M + m)
v2It is found that (M + m) v2 = mghConclusionThe 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 Page 17 of 522.7 HOOKES LAW
Hypothesis:The bigger the weight, the longer the spring
extensionAim of the experiment:To determine the relationship
between the weight and the spring extensionVariables:Manipulated:
Weight of the load Responding: Spring extension Constant: Spring
constantApparatus and Materials: Spring, pin, weights, plasticine,
retort stand, metre ruleSetup: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, lis 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 Page 18 of 52Results:Original
length of spring = l0 = cmLoad mass(g)Load weight(N)Spring length,
l(cm)Spring extension, x = l l0(cm)
50 g0.5 N
100 g1.0 N
150 g1.5 N
200 g2.0 N
250 g2.5 N
Analysis:A graph of spring extension, x against weight, F is
plotted.xFThe 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 Page 19 of 52
CHAPTER 3:FORCES AND PRESSURE3.1 PRESSURE IN LIQUIDS
Experiment 1: Water pressure and depthHypothesis:Water pressure
increases with depthAim of the experiment:To find the relationship
between the pressure in a liquid according to its
depthVariables:Manipulated: Depth of liquid Responding: Pressure in
liquid Constant: Density of liquidApparatus and Materials:
Measuring cylinder, thistle funnel, rubber tube, manometer, metre
ruleSetup: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 Page 20 of
52Results: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
DepthConclusion: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 densityAim
of the experiment:To find the relationship between the pressure in
a liquid and its densityVariables:Manipulated: Density of liquid
Responding: Pressure in liquid Constant: Depth of liquidApparatus
and Materials: Measuring cylinder, thistle funnel, rubber tube,
manometer, metre rule, water, glycerin, alcoholChapter 3: Forces
and Pressure Page 21 of 52Setup: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 cmLiquidDensity (kg
m-3)Manometer reading (cm)
Water1000
Glycerin1300
Alcohol800
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 Page 22 of 523.2 ARCHIMEDES
PRINCIPLE
Hypothesis:The buoyant force on an object in a liquid is equal
to the weight of the liquid displacedAim of the experiment:To find
the relationship between the buoyant force acting upon an object in
a liquid and the weight of the liquid
displacedVariables:Manipulated: Weight of the objectResponding:
Buoyant force / Weight of liquid displacedConstant: Density of
liquid usedApparatus and Materials: Eureka tin, spring balance,
stone, thread, beaker, triple beam balanceSetup: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. Thebeaker 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 Page 23 of 52
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
isrecorded.Results:Weight of stone in air = W1Weight of stone in
water = W2Buoyant force acting on the stone = W2 W1Weight of the
empty beaker = m1gWeight of the beaker and displaced water =
m2gWeight of the displaced water = (m2 m1)gIt is found that W2 W1 =
(m2 m1)gDiscussion: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 ofwater displaced.Conclusion:Buoyant force on
the stone = Weight of the water displaced by the stoneHypothesis
proven.Note: Experiment can be modified to compare the weight of
different sized stones and the values of buoyant force3.3 PASCALS
PRINCIPLE
Hypothesis:The liquid pressure exerted on a small surface is
equal to the liquid pressure exerted on a large surface in a closed
systemAim of the experiment:To find the relationship between the
pressure in a small syringe and a large syringe in a closed
systemVariables:Manipulated: Pressure acting on the small syringe
Responding: Pressure acting on the large syringe Constant: Density
of liquid within the systemChapter 3: Forces and Pressure Page 24
of 52Apparatus and Materials: 5 ml syringe, 10 ml syringe, several
weights, rubber tube, two retort standsSetup: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 sizeCross-sectional area,
AMass of the weight, mForce exerted on the syringe, F = mgPressure,
P= F A
SmallA1m1F1P1
LargeA2m2F2P2
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
waterpressure 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 Page 25 of 523.4 BERNOULLIS
PRINCIPLE
Hypothesis: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
fluidVariables:Manipulated: Velocity of the water Responding:
Pressure of the water Constant: Density of the waterApparatus and
Materials: Uniform glass tube, Venturi tube, rubber hose, water
from a tapProcedure: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 stopperChapter 3: Forces and
Pressure Page 26 of 52Venturi tube:
With the stopper Without the stopperDiscussion: 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, thereforethe 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 tolow pressure.Conclusion:The higher the water velocity,
the lower the pressure at that point. Hypothesis proven.Chapter 3:
Forces and Pressure Page 27 of 52
CHAPTER 4:HEAT AND ENERGY4.1 SPECIFIC HEAT CAPACITY
Experiment 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 heatAim of the
experiment:To determine the rise in temperature of water with
varying massesVariables:Manipulated: Mass of water, m Responding:
Rise in temperature, Constant: Amount of heat supplied, QApparatus
and Materials: Beaker, electric heater, thermometer, stopwatch,
triple beam balance, stirrer, polystyrene sheet, felt clothSet
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.
TheChapter 4: Heat and Energy Page 28 of 526. 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.8. A
graph of against m and a graph of againstResults:
1 are plotted.mMass of water,m (kg)Initial temperature, 1
(C)Final temperature, 2 (C)Rise in temperature, = 2 1 (C)1
(kg-1)m
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 sameperiod 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 greaterAim of
the experiment:To determine the rise in temperature of water with
varying amounts of heatVariables:Manipulated: Amount of heat
supplied, Q Responding: Rise in temperature, Constant: Mass of
water, mChapter 4: Heat and Energy Page 29 of 52Apparatus and
Materials: Beaker, electric heater, thermometer, stopwatch, triple
beam balance, stirrer, polystyrene sheet, felt clothSet
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 definedoperationally as the heat quantity. The
following graph is obtained:Chapter 4: Heat and Energy Page 30 of
52
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 aluminiumApparatus and Materials:
Aluminium cylinder, weighing scale, electric heater, thermometer,
power supply, felt cloth, polystyrene sheet, stopwatch, lubricating
oilSet 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 Page 31 of
52Results:Electric power of heater = P WattHeating time = t
secondsMass of aluminium cylinder = m kgInitial temperature of the
aluminium cylinder = 1Final temperature of the aluminium cylinder =
2Temperature rise = 2 1Electrical energy supplied by the heater =
PtHeat energy absorbed by the aluminium cylinder = mcOn the
assumption that there is no heat loss to the surroundings: Heat
supplied = Heat absorbedPt = mcSpecific heat capacity, c = Pt
mDiscussion: The aluminium cylinder is wrapped with a felt cloth to
reduce the heat loss to thesurroundings 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 experimentis 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 electricalheater 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 HEAT
Experiment 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 suppliedAim of the
experiment:To observe the change in temperature when naphthalene is
meltingApparatus and Materials: Boiling tube, naphthalene powder,
beaker, thermometer, Bunsen burner, stopwatch, retort stand, tripod
stand, wire gauzeChapter 4: Heat and Energy Page 32 of 52Set
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 thenaphthalene starts to melt. The naphthalene starts
to melt at 80C. The temperature remains constant at this valuefor
several minutes while the naphthalene continues to melt with the
heat.Chapter 4: Heat and Energy Page 33 of 52 After the naphthalene
has completely melted, the temperature begins to rise withcontinued
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
temperatureAim of the experiment:To observe the change in
temperature when naphthalene is freezingApparatus and Materials:
Boiling tube, naphthalene powder, beaker, thermometer, Bunsen
burner, stopwatch, retort stand, tripod stand, wire gauzeSet
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 temperaturedrops to about 60C.5. A graph of temperature
against time is drawn.Chapter 4: Heat and Energy Page 34 of
52Results: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 until80C 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 iceApparatus and Materials: Pure ice, electric immersion heater,
filter funnel, beaker, stopwatch, weighing balance, power supply,
retort stand, clampChapter 4: Heat and Energy Page 35 of 52Set
up:Set A Set BProcedure: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
kgMass of beaker + water = mA2 kgMass of ice melted by surrounding
heat, ma = mA2 mA1 kgSet B:Mass of empty beaker = mB1 kgMass of
beaker + water = mB2 kgMass of ice melted by surrounding heat &
immersion heater, mb = mB2 mB1 kgMass 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 = mLAssuming there is no heat loss to the
surroundings:Electrical energy supplied = Heat energy absorbed by
the melting icePt = mLSpecific latent heat of fusion of ice, L = Pt
mChapter 4: Heat and Energy Page 36 of 52Discussion: The purpose of
Set A, the control experiment, is to determine the mass of ice
meltedby the surrounding heat. The immersion heater must be fully
immersed in the ice cubes to avoid or reduce heatloss. The
stopwatch is not started simultaneously when the immersion heater
is switchedon 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 ishigher 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 waterApparatus and Materials: Pure water,
electric immersion heater, filter funnel, beaker, stopwatch,
weighing balance, power supply, retort stand, clampSet
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 Page 37 of 52Results:Electrical power
of heater = P WattTime period of boiling = t secondsElectrical
energy supplied by the electrical immersion heater, E = PtMass of
water vapourised = m2 m1Heat energy absorbed by the water during
vapourisation, Q = mLAssuming there is no heat loss to the
surroundings:Electrical energy supplied= Heat energy absorbed by
the vapourized waterPt = mLSpecific latent heat of vapourization of
water, L = Pt mDiscussion: The immersion heater must be fully
immersed in the water to avoid or reduce heatloss. The stopwatch is
not started simultaneously when the immersion heater is switchedon
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 thisexperiment 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 LAW
Option 1: Changing the volume of air to measure
pressureHypothesis:When the volume of air decreases, the pressure
increases when its mass and temperature is constantAim:To
investigate the relationship between the pressure and volume of
airVariables:Manipulated: Volume of air within syringeResponding:
Pressure of airConstant: Mass, temperature of airApparatus and
Materials: Rubber hose, Bordon gauge, 100 cm3 syringeChapter 4:
Heat and Energy Page 38 of 52Set 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 thegauge.4. The piston of the
syringe is pushed in until the trapped air volume becomes 90 cm3and
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)VPressure, P (Pa)
100
90
80
70
60
Analysis: A graph of P against
1 is plotted.V A linear graph going through the origin is
obtained. This indicates that pressure is inversely proportional
tothe volume of gas.Conclusion:Gas pressure of fixed mass is
inversely proportional to its volume.
Chapter 4: Heat and Energy Page 39 of 52Option 2: Changing the
pressure of air to measure volumeHypothesis:When the pressure of
air decreases, the volume increases when its mass and temperature
is constantAim:To investigate the relationship between the pressure
and volume of airVariables:Manipulated: Pressure of airResponding:
Volume of air trapped in the capillary tubeConstant: Mass,
temperature of airApparatus and Materials: Bicycle pump, ruler,
tank with oil, pressure gauge, glass tubeSet 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 Page 40 of
52Results:Pressure, P (kPa)1 (Pa-1)PVolume, V (cm3)
10
20
30
40
Analysis: A graph of V against
1 is plotted.P A linear graph going through the origin is
obtained. This indicates that pressure is inversely proportional to
thevolume of gas.Conclusion:Volume of gas of fixed mass is
inversely proportional to its pressure.4.4 CHARLES LAW
Hypothesis:When the temperature of air increases, the volume
increases if the mass and pressure is constantAim:To investigate
the relationship between the volume and the temperature of
gasVariables:Manipulated: Air temperatureResponding: Air
volumeConstant: Mass and pressure of the trapped airApparatus and
Materials: Capillary tube, tall beaker, thermometer, Bunsen burner,
tripod, wire gauze, retort stand, mercury or concentrated sulphuric
acid, stirrer, ruler, ice, rubber bandChapter 4: Heat and Energy
Page 41 of 52Set 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 columnis recorded every 10 C until the water temperature
reaches 90 C.Results:Temperature, (C)102030405060708090
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 Page 42 of 52Discussion: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 temperature4.5 PRESSURE LAW
Hypothesis:When the temperature of air increases, the pressure
increases if the mass and volume is constantAim:To investigate the
relationship between the pressure and the temperature of
gasVariables:Manipulated: Air temperatureResponding: Air
pressureConstant: Mass and volume of the trapped airApparatus and
Materials: Round-bottomed flask, mercury thermometer, Bourdon
gauge, Bunsen burner, tripod, wire gauze, retort stand, stirrer,
iceSet up:
Chapter 4: Heat and Energy Page 43 of 52Procedure: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 80C.Results:Temperature, (C)304050607080
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 temperatureChapter 4: Heat and Energy
Page 44 of 52
CHAPTER 5:LIGHT AND VISION5.1 REFLECTION
Hypothesis:The angle of reflection is equal to the angle of
incidenceAim of the experiment:To study the relationship between
the angle of incidence and angle of
reflectionVariables:Manipulated: Angle of incidence, i Responding:
Angle of reflection, r Constant: Plane mirror
usedApparatus/Materials: Light box, plane mirror, plasticine,
paper, pencil, protractorSetup: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 Page 45 of 52Results:Incident angle ()Reflected angle
()
15
30
45
60
75
Conclusion:The angle of incidence is equal to the angle of
reflection.5.2 CURVED MIRRORS
Aim of the experiment:To study the characteristics of images
formed by curved mirrorsApparatus/Materials: Concave mirror, convex
mirror, plasticine, light bulb mounted on a wooden block, metre
rule, white screenSetup: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 themirror, 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 Page 46 of 525. 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
objectObject distance, u (cm)Image distance, v (cm)Characteristics
of image
Real / VirtualUpright / InvertedDiminished / Magnified / Same
size
Beyond C(u > 2f)
At C(u = 2f)
Between Cand F(f < u < 2f)
At F(u = f)
Between Fand P(u < 2f)
Convex mirrors:For all positions, the image characteristics
are:
Conclusion: For concave mirrors, images formed can be real or
virtual, whereas for convexmirrors, only virtual images are formed.
The characteristics of images formed by the concave mirror depend
on the position ofthe object.5.3 REFRACTION
Hypothesis: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 isin r
is aAim of the experiment:To study the relationship between the
angle of incidence and angle of refractionChapter 5: Light and
Vision Page 47 of 52Variables:Manipulated: Angle of incidence, i
Responding: Angle of refraction, r Constant: Plane mirror
usedApparatus/Materials: Ray box, glass block, paper,
pencilSetup: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.7. The values of sin i, sin r, and
sin isin r
are calculated.Results:Angle of incidence, i ()Angle of
refraction, r ()Sin iSin rn = sin isin r
20
30
40
50
60
Conclusion:It is found that
sin isin r
is a constant. Hypothesis valid.Chapter 5: Light and Vision Page
48 of 525.4 ACTUAL DEPTH & APPARENT DEPTH
Hypothesis:The deeper the actual depth, the deeper the apparent
depthAim of the experiment:To study the relationship between the
actual depth and apparent depthVariables:Manipulated: Actual depth,
DResponding: Apparent depth, dConstant: Refractive index of medium
(water), nApparatus/Materials: Tall beaker, 2 pins, ruler, metre
rule, retort standSetup:
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 Page 49 of 52Results: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.DdDiscussion: The gradient of the graph is equal to the
index of refraction of water.Conclusion: Hypothesis is valid5.5
TOTAL INTERNAL REFLECTION
Aim of the experiment:To determine the critical angle of
glassApparatus/Materials: Semicircular glass block, ray box,
protractor, white paper, pencilSetup: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 522. The glass block is put aside. A
normal line, NN is drawn through the centre point, Oon 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 rayis 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 reflectedback 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 reflectedwithin the glass
blockAnalysis:The critical angle, c is a constant.Refractive index
of glass, n =
1sin cConclusion:The refractive index of glass, n =
1 sin c5.6 LENSES
Hypothesis: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,
fApparatus/Materials: Cardboard with a cross-wire in triangular
cut-out, light bulb, lens holder, convex lens, concave lens, white
screenChapter 5: Light and Vision Page 51 of 52Setup: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
of objectObject distance, u (cm)Image distance, v
(cm)Characteristics of image
Real / VirtualUpright / InvertedDiminished / Magnified / Same
size
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 theobject.Chapter 5: Light and Vision Page 52 of
52