1 MONASH UNIVERSITY FOUNDATION YEAR PHYSICS 2 CHAPTER 1: OPTICS REVISION 1.1 Measurements and Units Quantities that can be measured are called ______________ quantities. Examples of physical quantities are like length, time, weight, current and many more. Two things need to be mentioned while stating a physical quantity. First is the ______________value, second, is the ______________ According to the Systeme’ International (S.I.), seven physical quantities has been selected to be the base quantity. The units for base quantities are called base units. Each fundamental quantity in the metric system is defined in terms of a naturally-occurring phenomenon, except for the mass standard. Base Quantity Base Units Name Symbol Name Symbol Time Length Mass Temperature Electric current Amount of substance Luminous Intensity Other physical quantities other than the base quantities are called the _________________. All derived quantities are a combination of the base quantities. Physical Quantities Defined as Unit Special Name Density Momentum Force Pressure Work (Energy) Power Electrical Charge Potential difference Resistance
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MONASH UNIVERSITY FOUNDATION YEAR
PHYSICS 2
CHAPTER 1: OPTICS
REVISION
1.1 Measurements and Units
Quantities that can be measured are called ______________ quantities. Examples of physical
quantities are like length, time, weight, current and many more.
Two things need to be mentioned while stating a physical quantity. First is the
______________value, second, is the ______________
According to the Systeme’ International (S.I.), seven physical quantities has been selected to be the
base quantity. The units for base quantities are called base units.
Each fundamental quantity in the metric system is defined in terms of a naturally-occurring
phenomenon, except for the mass standard.
Base Quantity Base Units
Name Symbol Name Symbol
Time
Length
Mass
Temperature
Electric current
Amount of substance
Luminous Intensity
Other physical quantities other than the base quantities are called the _________________. All
derived quantities are a combination of the base quantities.
Physical
Quantities
Defined as Unit Special Name
Density
Momentum
Force
Pressure
Work (Energy)
Power
Electrical Charge
Potential difference
Resistance
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1.2 Prefixes
For very large or very small numbers of quantities, we can use standard prefixes with the base
units.
Prefix Multiplying Factor Symbol
Pico
Nano
Micro
Mili
Centi
Deci
Kilo
Mega
Giga
Tera
Example
Energy stored in a bowl of ice cream = 12 000 000J
= 12 x 106
= 12 MJ
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1.3 Significant Figures
To count the number of significant figures, you must count up the total number of digits starting
at the first non zero digit, reading from the left to the right.
Fill in the blanks below
Always give your answers to the lowest significant figures found in the question.
A zero is said to be significant if:
(1) it is between two non-zero digits 3001 m (4 s.f), 30.001 m (5 s.f)
(2) it is at the end of a decimal expression 0.00310 km (3 s.f)
(3) it is required when expressing the number in scientific notation 3.10 x 106 m (3.s.f)
Otherwise a zero is considered to be only a placeholder. 150,000 m all four zeros are placeholders 1.5 x 10
5 m
0.0015 km all three zeros are placeholders 1.5 x 10-3
km
150. Gm no zeros are placeholders
(note the deliberate inclusion of the decimal) 1.50 x 1011
m
Example: A swimmer covers a distance of 100.0m in 68s. Calculate her average speed.
Scientific Notation.
Express your value so that it has one digit to the left of the decimal and all other significant digits to the
right of the decimal. It should then be multiplied by an appropriate power of 10.
(1) When the absolute value of the original number is greater than one, then moving the decimal point
will require the resulting number to be multiplied by 10 raised to a positive exponent.
(2) When the absolute value of the original number is less than one, then moving the decimal point will
require the resulting number to be multiplied by 10 raised to a negative exponent.
3 s.f 2 s.f 1 s.f.
4.62
0.00504
3.40 x 108
169
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OPTICS
Definitions
Luminous : An object that ______________ its own light is said to be luminous eg. Stars
Illuminated : An object becomes ______________t when light falls on it is said to be
illuminated.
Transparent : An object that ______________ light to pass through it is said to be transparent.
Eg Glass
Opaque : Objects that ______________ light/ do not allow light to pass through are called
opaque. Eg Wooden Shutters
Translucent : An object that allows light to pass through although you cannot see
______________ them eg ______________
Diffuse Reflection and Specular Reflection
a) Specular reflection
When parallel light is incident upon a
smooth surface (eg. Mirror) the reflected
rays are parallel to each other.
b) Diffused Reflection
When parallel light is incident upon a
rough surface, the reflected rays are in
various direction.
Light Ray and Light Beam
Light ray is a narrow band of light energy drawn as a straight line
Light beam is a collection of rays
Spectrum
A range of colours produced when white light is dispersed through a prism.
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Rectilinear Propagation of Light
The property of light traveling in straight lines.
Because of this, a few phenomena can be seen to happen.
i) Shadow- shadows mostly tell us about the nature of light. Light tends to travel in straight
lines and can be blocked by material objects. It doesn't bend around them and fill in the
area behind, at least at the scale we are considering here.
ii) Parallax is a displacement or difference in the apparent position of an object viewed along
two different lines of sight. Parallax creates ______________ through observed changes as you
move. Close one eye so that you are only looking through one lens. Hold out your thumb in
between you and another object, such as this Physics notes. There is some part of the notes that is
obscured by your thumb. However by moving your head, you can see around the thumb to the
pages. When your brain uses parallax, it gauges the relative movement of two objects as you
move, which will describe the relative distance between you and the two objects.
When an observer moves, the apparent relative motion of several stationary objects against a
background gives hints about their relative distance. If information about the direction and
velocity of movement is known, motion parallax can provide absolute depth information. This
effect can be seen clearly when driving in a car. Nearby things pass quickly, while far off objects
appear stationary.
A simple everyday example of parallax can be seen
in the dashboard of motor vehicles that use a needle-
style speedometer gauge. When viewed from directly
in front, the speed may show exactly 60; but when
viewed from the passenger seat the needle may
appear to show a slightly different speed, due to the
angle of viewing.
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iii) The discovery of the Pin-Hole Camera
A pinhole camera is the simplest camera possible. It consists of a light-proof box, some sort of
film and a pinhole. The pinhole is simply an extremely small hole like you would make with the
tip of a pin in a piece of thick aluminum foil.
A pinhole camera works on a simple principle.
Imagine you are inside a large, dark, room-
sized box containing a pinhole. Imagine that
outside the room is a friend with a flashlight,
and he is shining the flashlight at different
angles through the pinhole. When you look at
the wall opposite the pinhole, what you will
see is a small dot created by the flashlight's
beam shining through the pinhole. The small
dot will move as your friend moves his
flashlight. The smaller the pinhole (within
limits), the smaller and sharper the point of
light that the flashlight can creates.
Now imagine that you take your large, dark, pinhole-equipped room outside and you point it at a
nice landscape scene. When you look at the wall opposite the pinhole, what you will see is an
inverted and reversed image of the scene outside. Each point in the scene emits light, and, just
like the flashlight, the beam of light from that point passes through the pinhole and creates a point
of light on the back wall. All of the points in the scene do that at the same time, so an entire
image, in focus, is created on the back wall of the room. The image is very dim because the
pinhole is so small, but you can see it if the room is very dark.
A pinhole camera is simply a smaller version of that room, and the film inside the camera
replaces you. The film records the image that comes in through the pinhole. The camera records a
nice, in-focus image of the scene that you point the camera at. Usually, you have to expose the
film for a long time because the pinhole lets so little light through.
Let’s try to draw the path of light ray on the space below to show how pinhole camera works.
Why the image is inverted?
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Common Useful Cases which light interacts with matter
CCD (charge coupled device) and Photoelectric Cells
Photoelectric materials are light sensitive materials which releases an electron when light is shone on it.
Digital cameras and scanner make use of CCD to produce images from the environment. CCD is a large
scale integrated circuit which containing hundred to thousands of photosites (pixels). The CCD photosites
accomplish their task of sensing incoming light through the photoelectric effect and subsequently
emitting the signal that results in a digital image. The photoelectric material is able to produce an image
because of the fact that some colours reflect more light than the other. (i.e white reflects light while black
absorbs it)
Bleaching by UV Light
Bleaching materials/soap powder will have fluorescent components in it. When fluorescent components
are exposed to UV light, it will absorb the energy and emit bright light. That’s why most soap powder can
promise shining white clothes.
Photosensitive Cells in the Eye
The very back of the eye is lined with a layer called the retina which acts very much like the film of the
camera. The retina is a membrane containing photoreceptor nerve cells that lines the inside back wall of
the eye. The photoreceptor nerve cells of the retina change the light rays into electrical impulses and send
them through the optic nerve to the brain where an image is perceived.
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The Electromagnetic Spectrum
Characteristics of the Electromagnetic Spectrum
All electromagnetic radiation has fundamental properties and behaves in predictable ways according to
the basics of wave theory. Electromagnetic radiation consists of an ______________which varies in
magnitude in a direction perpendicular to the direction in which the radiation is traveling, and a
______________ oriented at right angles to the electrical field. Both these fields travel at the
______________ (c).
Ultraviolet (UV) - ____________________________radiation given off by electrical discharges,
such as sparks and lightning. It is also given out by stars such as our Sun. The
ozone layer in our atmosphere absorbs UV with wavelength less than 300nm but
its revent thinning increases the risk of skin cancers.
Visible light - ______________but other animals have eyes sensitive to different ranges. Eg.
Bees can see ultra violet.
Infra-red (IR) -is produced by all hot bodies. Common usage: ______________.
Radio Waves - can range from a wavelength of ______________. For mobile phones the
wavelength of radio waves used are about 1m. Radio waves less than 1m are used
for satellites, GPS, deep space probe whereas radio waves more than 1m is used
for radio and TV transmission.
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X-Rays - high energy waves which is dangerous to humans if they are exposed long term.
Gamma Rays - Gamma rays were discovered by P. Villiard in 1900. These are the most energetic
photons, apart from Cosmic rays. Thanks to their penetrative ability, gamma rays is
widely used in medicine. (eg radiotherapy- to divide cancerous cells etc.)
Dangers of being exposed to high energy waves (i.e the UV, X-rays and Gamma Rays)
Medical men have been aware for half a century that X rays can be destructive to human tissue.
Overdosage of X rays for benign purposes can have malignant consequences. Example: careless
treatment may cure acne, but cause skin cancer. Despite this established knowledge, X rays are still being
incautiously used as cure-alls. In the New England Journal of Medicine, Drs. Bradford Cannon, Judson
G. Randolph and Joseph E. Murray of Boston report that "patients continue to appear with permanent
tissue destruction that has resulted from relatively recent radiation treatment of acne, plantar wart,
eczema [and] superfluous hair." Examining 165 such cases from their personal files and the records of
Massachusetts General Hospital, the doctors starkly document the dangers of unnecessary exposure to
irradiation.
Items:
¶ Nearly half the patients suffered from persistent painful ulceration.
¶ Cancer appeared in 36—or 22%—of the cases.
¶ Of the ten patients who had been treated for acne, nine developed skin cancer.
"This appears to be an increasing problem," warn the doctors, "since twice the number were observed at
the Massachusetts General Hospital in the decade 1948 to 1957 as in the preceding decade." But the
worst may be yet to come. No one knows how many healthy people with histories of such treatment may
later develop malignancies. The interval for the appearance of cancer after treatment ranged in the study
Parallel - When two mirrors are parallel to each other, the number of reflections is ______________.
Placing one mirror at a slight angle causes the reflections to curve.
Click to enlarge
Multi-Faceted Mirrors - Increasing the number of flat mirrored surfaces or facets increases the number
of reflections, but what you see depends on where you stand. The number of complete and partial reflections changes as you view the mirror from different angles.
Reflectors on cars and Bicycle
Night reflectors glow when any light falls on them
Night or bicycle reflector
The ray of light incident on the
reflector are sent back in the same
direction
Total internal reflection takes place inside a reflector