Unit 3
Light and Optical
Systems
Name:____________________
1
Topic 1 What is light?
What is light?
- Form of energy that you can see
- It comes from both natural and artificial sources
- Natural Sources
o Sun, stars, fire
o These objects radiate (give off) light in all directions
 Light energy is called Radiation or radiant energy
- Artificial Light Sources
o Light bulbs
 radiate light in all directions
- Light is made up of small particles called photons
(small bundles of energy) which can be transformed into other
types of energy
The brighter the light source (Intensity), the more photons there are, meaning more
energy can be transformed!
-Incandescent Sources
o Heating an object to a high temperature until it emits light
ex. 100 W light bulb (the filament in the bulb becomes so hot that it
glows.
Fluorescent Sources
Electrical Energy absorbed byUltraviolet light  Energy absorbed  Visible light
Energy
mercury particles
Energy
by particles
energy
-How it works
 Electric current causes mercury vaporize inside the tube and
gives off ultraviolet energy
 The phosphor coating on the inside of the tube absorbs the
ultraviolet energy
 The coating glows, producing light immediately!
 Hard to dispose of because of the mercury in the tubes. Mercury is
toxic.
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- Phosphorescent Sources
o Light energy is stored by certain particles and released as visible
light later.
 Glow in the dark objects!
- Chemiluminescent Sources
o Light can be released by chemical reactions.
 Glow Sticks
- Bioluminescent Sources
o Light emitted from living things
 The light is emitted from chemical reactions inside living
things.
ex. Deep sea fish
- All objects that emit light are called luminous!
o Ray (Wave) Model
 A ray is a straight imaginary line that represents the path of
a beam of light.
 Explains shadows
 The light cannot bend around an object.
 Can also explain how light behaves around certain objects
 Transparent
o Light rays can pass through without being
affected
 Glass, air, lenses of your eyes
 Translucent
o The rays are deflected or bend around the
object (but you can still see the light… but not
the objects behind it)
 A piece of paper to a light source
 Opaque
o Casts shadows behind. The light rays are totally
blocked.
 Thick text books, humans etc.
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Calculating the cost of lighting Notes
Step 1: Convert watts (W) to kilowatts (kW)
(W/1000) = x
Step 2: Multiply kW by hours (X times # of hours) = kW∙h
Step 3: # of kilowatt hours x cents per hour = $ amount per hour
of lighting
1. If you have a 60W light bulb, and it will cost 10 cents per kWh, how much will it cost if
we leave the bulb on for 13 hours?
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Name _________________
Practicing Calculating the Cost of Lighting
Show your work and all the units.
1. If you have a 55W bulb in an overhead machine and it costs 35cents per
kWh, how much will it cost if we run the machine for 2 hours?
2. If you have a 18W bulb in a smartboard projector and it costs 50cents per
kWh, how much will it cost if we run the projector for 8 hours?
3. If you have a 20W bulb in a night light and it costs 55cents per kWh, how
much will it cost if we keep the light on for 8 hours?
4. If you have a 35W bulb in a lamp and it costs 45cents per kWh, how much
will it cost if we keep the lamp on for 3 hours?
5. If you have 8 100W bulbs in a chandelier and it costs 40cents per kWh, how
much will it cost if you leave the chandelier on for 6 hours?
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6. If electrical energy costs 8 cents per kWh, calculate the cost of running a
15W scanner for an hour.
7. If electrical energy costs 20 cents per kWh, calculate the cost of running a
50W bulb in a photocopying machine for 30min. (use cross multiplying to
change minutes to hours.)
8. If you have a 60W bulb in a lamp and it costs 60cents per kWh, how much
will it cost if we keep the lamp on for 4 hours?
9. If electrical energy costs 16 cents per kWh, calculate the cost of running a
47W bulb in a photocopying machine for 45min. (use cross multiplying to
change minutes to hours.)
10.If electrical energy costs 12 cents per kWh, calculate the cost of running a
30W bulb in a light fixture for 10min. (use cross multiplying to change
minutes to hours.)
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Topic 1 Review
1. What is Light?
_____________________________________________________________
_____________________________________________________________
2. Write the energy path way for :
a. Incandescent source.
___________________________________________________________
b. Fluorescent source.
___________________________________________________________
___________________________________________________________
c. A chemiluminescent source
___________________________________________________________
3. State one advantage that fluorescent tubes have over incandescent lights
blubs?
4. If electrical energy costs 7¢/kW•h, calculate the cost of running a 15 W
scanner for 10 minutes. ( You will need to convert 10 min into hours.)
5. Describe what happens when light strikes: A. translucent material, B.
transparent material C. Opaque material. Give an example of each type of
surface.
A._________________________________________________________
B._________________________________________________________
C._________________________________________________________
6. A. What would happen to the intensity of sunlight if earth were twice as far
from the sun?
________________________________________________________________
________________________________________________________________
B. What would consequences be on earth if that was the case? Why?
________________________________________________________________
________________________________________________________________
________________________________________________________________
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Topic 2 “Reflection”
Reflection - the process in which light strikes a surface and
bounces back off that surface.
- the difference between seeing your own image and seeing a
printed page is determined by the surface from which light
reflects.
Incident ray – the ray that comes from a light source and
strikes the surface
Reflected ray – the ray that bounces off the surface
Draw the picture on page 189.
The Law of reflection – the angle of reflection = the angle of incidence.
-light travels in straight lines
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 Smooth surfaces reflect light very uniformly.
 Rough surfaces reflect light very scattered since the
normal lines point in different directions. This causes the
reflected rays to be scattered and cannot form an image.
-Convex mirror – mirror that curve outward (have a bulge)
-Concave mirror – mirror that curves inward (caves in like a shiny bowl)
Read pg. 188-199
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When Light Reflects Lab
Follow instructions on pg. 192-193
Write a hypothesis using the question on the top of page 192.
Hypothesis : ___________________________________________
_____________________________________________________
_____________________________________________________
Step 3
Drawing #1
Step 6
Drawing #2
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Analyze
1. A. In steps 4 and 6, what happened to some of the light that
struck the lower flat surface between the air and the water?
B. What common object replicates the behaviour of this light?
A._______________________________________________
_________________________________________________
B. _______________________________________________
2. A. In step 7 what change occurred on the surface of the water
when you tapped on the glass?
B. Could you still see the reflection of the pencil? Why?
A. __________________________________________________
____________________________________________________
B. ___________________________________________________
_____________________________________________________
_____________________________________________________
3. During reflection, what happens to the direction in which light
travels? Be specific.
___________________________________________________
___________________________________________________
___________________________________________________
___________________________________________________
___________________________________________________
___________________________________________________
Did you observations support or refute your hypothesis? Explain.
___________________________________________________
___________________________________________________
___________________________________________________
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See What You Get
What to Do
1. Use a ruler to draw the reflected images of the objects below.
2. Were there any differences between the object and its image in the plane mirror? Describe
any differences, with respect to
(a) size
(b) distance from the mirror
(c) orientation
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Mirror Images
What to Do
Use a mirror to read the three messages below. Then answer the following questions.
1. Which of these messages is a true reflection in a plane mirror?
2. How were the other messages made?
3. What capital letters look the same in the mirror?
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Topic 2 Review
1. A. Make a simple drawing in which you show and label: an incident
ray, a reflected ray, the normal, the angle of incidence and the
angle of refraction.
B. Write a definition of each.
A.
B. _______________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
2. State the law of reflection.
_________________________________________________
_________________________________________________
_________________________________________________
3. When you see the reflection of the tip of your nose in a plane
mirror, where are the reflected rays of light coming from?
_________________________________________________
_________________________________________________
_________________________________________________
4. What happens to light when it bounces off a rough surface?
_________________________________________________
_________________________________________________
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5. Complete the measurements and draw the missing parts.
Use Pencil.
a.
B.
c.
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Topic 3 - Refraction
Refraction- is the bending of light when it travels from one medium to another.
Light bends because it changes speeds when going through materials with different
densities.
The bending of light makes objects appear to be in a different position from where
it really is.
Bending Light
When light enters from one medium to a more dense medium, it will bend toward
the line of normal. Example light entering water.
When light leaves a denser medium, to one that is less dense, light bends away
from the line of normal. Example light leaving water.
The new direction of light is called the angle of refraction. (R)
When the angle of incident increases (i), the angle of refraction (R) as increases.
Refraction can also occur going through air at different temperature.
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The Re-appearing Coin Lab
Follow instruction on Pg. 200
When water was poured into the cup, you could see the coin, even
though the straight line path of the light was blocked by the cup.
1. Indicated the water line and draw rays to show the light’s
path. Use pencil.
2. What happened to the rays of light when the light passed from
the air to water?
_______________________________________________
_______________________________________________
_______________________________________________
_______________________________________________
_______________________________________________
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When Light Refracts Lab
Follow instructions on pg. 201
Step 1
Drawing #1
Step 2
Drawing #2
Step 3
Drawing #3
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Analyze
1. A. In step 1, through what medium did the light from the ends of
the pencil travel before reaching your eyes?
____________________________________________
b. Through what medium did the light from the middle of the
pencil have to travel?
________________________________________________
c. Did the light travel straight in any of the mediums in step 1?
Which medium(s)?_________________________________
2. A. In steps 2 and 3, through which medium does the light from
the bottom part of the pencil travel before reaching your eyes?
________
b. What happens to the path of the light when it moves from the
water to the air? ____________________________________
__________________________________________________
__________________________________________________
3. Through how many different mediums does the light travel
through in this activity? _________________________
4. What can happen to the path of the light during refraction?
What can happen to the image you see, compared with the real
object?
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
Study Topic 1-3 Quiz
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Topic 3 Review
1. What is the difference between reflection and refraction?
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
2. Give two examples of materials that mostly refract light. Is light also
reflected or absorbed by these materials?
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
3. What happens to light when it is refracted?
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
4. Using the normal as a reference line, describe the change in direction of a
light ray the travels from,
a. Air into glass. ______________________________________________
___________________________________________________________
b. Water into air. _______________________________________________
_____________________________________________________________
5. Trace the following diagram using a ruler and pencil.
6. Describe the changes if instead of traveling 300 000km/s in air, light
travelled only at the speed of a car on a highway, about 0.03 km/s?
_____________________________________________________________
_____________________________________________________________
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Topic 4
Lens  a curved piece of transparent material
ex. Glass
Double Concave  Light passing through the thicker more
curved part of the lens causes light to bend
Double Convex lens  thicker in the middle
 causes the refracting light to come together or converge
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Eye Spy
In a normal eye, light refracts through the lens onto a light sensitive area at the back of the eye called the retina and the
image you see is formed on the retina.
- Near-sighted – when your eyes are too long and an image
forms in front of the retina. These people have trouble seeing
things that are far away.
- Far- sighted- when your eyes are too short an image forms
behind the retina. These people have trouble seeing things
that are too close to them.
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Compare the Eye with the Camera
Camera
Human Eye
-diaphragm – device
that control the
aperture (the
opening) of a lens or
optical system
-Iris- colored
Both control the
ring that controls size of opening
how much light
enters the pupil
-shutter-
-Iris reflex –
- aperture- the
opening of the
camera
Both:
Limits the
passage of light
-Pupil – the
Both are the
opening of the eye opening
-Film- chemical
change occurs to
record the image
-Retina- senses
light and
produces small
electrical
impulses that
travels from the
retina to the
brain
- Light proof boxcontains the parts of
the camera
Lens
- tissue – contains
the parts of the
eye
Lens and Cornea
Both detect
light
Both focus the
light into a real
image
-Blind spot – the point where the optic nerve enters the retina
- has no light sensing cells
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Near and Farsighted Lab
http://www.learnalberta.ca/content/tlfrbl/index.html?launch=true
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Topic 4 Review
1. As an object comes closer to a convex lens what happens to the
size of the image?
_________________________________________________
2. Draw a diagram to show what happens when light passes through:
a. A concave lens
b. a convex lens
3. Make labelled drawings to show how the lens in a pair of glasses
can be used to correct:
a. Far- sightedness
b. near-sightedness
4. Describe 3 ways in which the human eye and a camera are similar.
Explain.
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
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Telescopes
Topic 5
Extending Human Vision
Refracting telescopes- has a convex lens to collect and
focus light from a distant object
- has an eyepiece lens to magnify the
Image
Reflecting telescope- has a concave mirror to collect rays
of light from a distant object
Binoculars- 2 reflecting telescopes mounted side by side
- using prisms, light is reflected back and forth inside a
short tube.
Microscopes- used to study genetic make-up or cancer.
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The Source of Colors
Sir Isaac Newton concluded:
- Different colors must be present in
white light
- white light is the result of mixing
together all different colors of light
spectrum → pattern when white light is
refracted into different colors
ex. rainbow
Colors of the solar spectrum
R red
O orange
Y yellow
G
green
B
I
V
blue
indigo (purple/blue)
violet
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- All colors are absorbed into the object
except the color you see.
- when white light passes through a blue
bottle, the glass absorbs all the colors
except blue. Only blue light is reflected!
- When all colors are absorbed you see black
- Additive Primary Colors – red, green and blue
- when you add all three colors together
in the proper amounts it makes white light
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-Secondary colors – 2 primary colors mixed
together - yellow, cyan, magenta
How we see color
The retina contains cells that respond to light
- rods- presence of light
- cones- color
-Color blindness – cones cannot detect color
Colour Blindness Test
http://colorvisiontesting.com/ishihara.htm
Study for Topic 4-6 Quiz
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Grade 8 Topic 6 Pg 232
Spotlight on Color
-Turn on all three floodlights (1 red, 1 green, 1 blue)
-try to produce a glowing patch of white light, change the brightness of each color by
moving floodlights closer or farther away. Is it possible?
1.) How close did you get to producing white light just using red, green, and blue
light?
2.) What happens when you shine a red light on a red object?
3.) What happens when you shine a red light on a blue object?
4.) What happens when you shine a red light on a green object?
5.) What happens when you shine a red light on a yellow object?
6.) What happens when you shine a green light on a red object?
7.) What happens when you shine a green light on a blue object?
8.) What happens when you shine a green light on a green object?
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9.) What happens when you shine a green light on a yellow object?
10.) What happens when you shine a blue light on a red object?
11.) What happens when you shine a blue light on a blue object?
12.) What happens when you shine a blue light on a green object?
13.) What happens when you shine a blue light on a yellow object?
14.) Why do the colors produced follow the rules of mixing primary colors?
14.) Name the color that is produced when combining green and blue light on the
wall.
15.) Name the color that is produced when combining red and blue light on the wall.
16.) Name the color that is produced when combining red and green light on the
wall
17.) Try to explain the colors that you saw in the shadows of your hand
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Topic 6 Review
1. What is a spectrum?
_________________________________________________
_________________________________________________
2. Why does grass look green or a rose look red?
_________________________________________________
_________________________________________________
_________________________________________________
3. What determines a colour of an object?
_________________________________________________
_________________________________________________
4. If green light and blue light are combined what colour is
produced? ______________________
5. If blue light and red light are combined what colour is
produced? ______________________
6. If a red object was hit with red light what colour would the
object appear?__________________
7. If a blue object was hit with red light what colour would the
object appear? _________________
8. If a blue object was hit with red light what colour would the
object appear? _________________
9. If a yellow object was hit with red light what colour would the
object appear? _________________
10. Explain how the two types of cells in the retina of the
human eye respond to light?
_________________________________________________
_________________________________________________
_________________________________________________
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Topic 7
The Wave Model of Light
- Dutch scientist Christiaan Huygens proposed
that light travels in waves.
- Crest – high part of the water
- Troughs – low parts of the water
- Wavelength – the distance from crest to
crest or trough to trough
o It is also measured as the distance
covered by one complete crest and trough
-Amplitude – the height of the crest or the depth
of the trough
- Frequency – the number of cycles in a certain
amount of time
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Wave Model of Light
- picture light traveling as a wave
- when light travels through a small opening the
waves spread out
- waves with short wavelengths spread out very
little
- waves with long wavelengths spread out more
Laser Light
- Theodore Maiman was the first physicist to
use laser light
- Incoherent light – waves work against each other,
waves of light are all jumbled. Crests of one wave
might overlap the troughs of another.
- ex. Incandescent light bulb
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-Coherent light – only one frequency or wave length.
Waves work together
- ex. Laser light
- What are lasers used for?
-scanners to read bar codes
-read data on CDs
-measure speed of cars
-cut through metal
-used as scalpels during surgery
-correct eye problems
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Gr 8, Unit 3
Topic 7, pg 240
Name:
Exploring Frequency and Wavelength
1) Hypothesis: Predict the effects on a wavelength when the frequency of a wave
changes (2 marks)
2) Draw a diagram of what you see when you hold the ends of the coil apart and moving one
end slowly. Label it “low-frequency wave”. Use arrows to show the directions in which the
marked coil moves. (3 marks)
3) Draw a diagram of what you see when you hold the ends of the coil apart and moving one
end quickly. Label this diagram. Use arrows to show the directions in which the marked coil
moves. (3 marks)
4) What happened to the wavelength of the coil when you moved the coil more quickly from
side to side? (2 marks)
5) As the coil wave travelled from one student to the other, in which direction did the marked
coil move? (2 marks)
6) Slow Waves in Water (bright rings are crests and dark rings are troughs) Draw a diagram
of what you see. Label your diagram (3 marks)
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7) Fast Waves in Water Draw a diagram of what you see. Label your diagram (3 marks)
8) What do you call the distance between the dark rings that you saw on the overhead
projector?
9) What happened to the wavelength of the water waves when you moved the pencil up and
down at a fast rate?
10) What happens to the size of the wavelength when the frequency increases?
11) What happens to the size of the wavelength when the frequency decreases?
12) In this investigation, what is the manipulated variable?
13) What is the responding variable?
14) How is frequency related to wavelength?
15) Did your observations support your hypothesis?
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Topic 7 Review
1. Draw a wavelength of 4cm and amplitude of 1cm. Label a crest,
a trough, the amplitude and the wavelength.
2. A buzzer vibrates 900 times in 1 sec. What is its frequency?
______________________________
3. A guitar string vibrates 880 times in 2 sec. What its
frequency? _____________________
4. Describe one way in which light behaves like a wave instead of
a particle.
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
5. Why do scientists prefer to talk about a wave model of light
instead of staying that light is a wave?
_________________________________________________
_________________________________________________
_________________________________________________
6. Jordan goes to a store and buys a pair of purple shoes that
match her purse perfectly. However when she got outside she
found that her shoes no longer match the purse well. Why
might this happen? Be specific.
_________________________________________________
_________________________________________________
_________________________________________________
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Topic 8 Beyond Light
-Different colors of light represent different frequencies and wavelength of light.
5 types of radiation
1) Infrared radiation- heat radiation
- used in heat lamps
- about 700nm
2) Radio waves- have a longer wavelength and the lowest
frequency in the electromagnetic spectrum
-microwaves have the shortest wavelength and the
highest frequency of all radio waves. They are
used in microwaves, and radar
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Remote Imaging Technologies
- RADARSAT - a Canadian satellite that
also produces radio waves
-monitors oil spills (locate environmental
damage)
- gathers data about floods
- and many more
-LANDSAT –Canadian satellite
-used to observe crops or forests
(monitor damage caused by insects
and disease)
-an many more
3) Ultraviolet Radiation- (UV)
-wavelength of 200nm
-very energetic (causes tanning)
-can damage cornea causing a slow loss of vision
-increase in UV is due to decrease in the ozone layer
caused by chemicals in aerosol spray cans. Freon gas
found in refrigerators and air conditioners also broke
down the ozone
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4) X-rays- shorter wavelength and higher frequencies
than UV
-very penetrating (pass through skin and muscle)
-extremely energetic
-used to locate broken bones, or look at wisdom
teeth
5) Gamma Rays – Shortest wavelength and highest frequency
of all waves in the electromagnetic spectrum
-nuclear reaction
-power to kill cells
-used to destroy tumors (radiation therapy)
 All of these waves are invisible
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Unit 3 Light and Optical Systems Study Guide
-What is light?
-2 types
What is radiation?
5 Sources of light
What is the ray model? Pg 184
What is the difference between transparent, translucent, and opaque?
What is reflection?
What is the difference between the reflected ray, incident ray, angle of incidence,
and angle of reflection?
What is a plane mirror?
Law of reflection
What happens when you look in a convex and concave mirror?
What is refraction? Apply your knowledge
Concave and convex lenses
Near-sighted and far-sighted
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How does your eye compare to a camera
Telescopes and binoculars
What is white light
Why do we see colors… Why do we see that my shirt is red?
Additive primary and Secondary colors
Cells in our eyes and what they do
What is colorblindness?
Wave model of light
What is laser light and why is it used?
Technologies such as infrared and UV radiation as well as x rays
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