Download Optics - The Study of Light

Name:_____________________________ Date:_______________ Period:______
Light and Color
By Sharon Fabian
The very first people on earth depended on sunlight. Sunlight allowed
them to see the world around them. Early people used sunlight to look for
food and to keep a lookout for dangerous animals or other people. Sunlight
has produced heat for the earth since earliest times. It is what plants use
to produce food in the process called photosynthesis. Sunlight also began
the process of forming our fossil fuels long before the first people arrived on earth.
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Sunlight was so popular that soon creatures on earth began finding ways to produce light for
themselves. Fireflies and a few other creatures produce their own light naturally. This is called
bioluminescence. People found ways to make light for themselves using campfires, candles, and oil
lamps. Later, gaslights were developed to light city streets. Even later electric lights were
developed. Today electricity provides most of our man-made light.
2
Light is a form of energy. It is one part of the whole spectrum of energy called the
electromagnetic spectrum. This type of energy is also called radiant energy. Besides light energy,
the electromagnetic spectrum also includes radio waves, microwaves, infrared waves, ultraviolet
waves, and other waves. The visible light part of the spectrum is the part that includes light that
humans can see. One interesting fact about the visible light spectrum is that it is not the same for
all creatures. For example, bees can see ultraviolet light, but they can't see the color red that we
see. Crocodiles miss out on a lot -- they can only see black, white, and shades of gray.
3
Most people can see the colors in the visible light spectrum that range from red to violet
(purple). These are the colors of the rainbow; starting with red, each one gradually blends into the
next color. The unusual name Roy G Biv is often used to remember the colors of the spectrum red, orange, yellow, green, blue, indigo, and violet.
4
One way to see the colors of light is by using a prism. A prism is a little piece of glass with
many sides that are cut at certain angles. A prism bends a ray of light and separates it into its
different wavelengths, or different colors. Sir Isaac Newton used prisms to make some important
discoveries about light way back in the 1600s.
5
There are many materials that let light pass through. In fact, materials can be grouped, or
classified, according to how well light passes through them. Materials such as a window that allow
light to pass through clearly are called transparent. Materials that let light rays pass through, but
mix them up so that we can't see clearly, such as frosted glass, are called translucent. Any
material that does not allow light to pass through is called opaque. A wooden board, a sheet of
construction paper, and a metal frying pan are all opaque.
6
Light from the sun, or from a flashlight, is called white light. It is a mixture of all of the
colors together. Light also has primary colors. The primary colors of light are red, green, and blue.
The colors can be combined to make other colors; for example, red plus blue produces magenta, a
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purplish color. Red plus green produces yellow. This is called color addition, because you are adding
colors of light together. You may be surprised to learn that mixing colors of paint or crayon is
called color subtraction. But it makes more sense once you know that paint and crayon actually
absorb certain colors of light. They subtract colors from the white light, leaving the remaining
colors for us to see.
Today, we still depend on sunlight just as much as the first people did, and we can also enjoy
the many beautiful colors it produces. Today we can also enjoy creating all kinds of artwork with
colors, thanks to color addition and color subtraction. What are some ways that you like to use
color?
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Copyright © 2007 edHelper
1. Light is a form of
Sound
Energy
Color
Heat
2. To remember the colors of the
spectrum, just remember the
name
Magenta
Roy G Biv
Leonardo
Isaac Newton
3. This is used to separate white
4. This is the name for the light that
5. Mixing colors of paint together is
6. Mixing colors together with
7. Describe an art project that you
8. You can experiment with color
light into colors.
Sunlight
Prism
Bioluminescence
Spectrum
called
Color subtraction
Color addition
have done, or would like to do, that
involves color subtraction.
fireflies produce.
Spectrum
Prism
Sunlight
Bioluminescence
colored pencils would be called
Color subtraction
Color addition
addition using a flashlight and
colored cellophane. Describe one
experiment that you could do.
Light and Color - Answer Key
1 Energy
2 Roy G Biv
3 Prism
4 Bioluminescence
5 Color subtraction
6
Color subtraction
7 Answers will vary.
8 Answers will vary.
Name:_____________________________ Date:_______________ Period:______
Optics - The Study of Light
By Sharon Fabian
If you wear glasses or contact lenses, you've probably been to the optometrist
for an eye exam. Maybe you bought your glasses or contacts from an optician. An
optometrist is someone who does eye exams to see if corrective lenses are needed,
and an optician is someone who makes and sells eyeglasses and contacts. Both of
these words, optometrist and optician, are forms of the word optic.
1
Optics is the branch of physics that involves the study of light. People who are
interested in optics study about how light is produced, how it is transmitted, how it is measured,
how it is detected, and how it is used. They study the visible light spectrum, which is the rainbow
of light that we can see from red to violet, and also ultraviolet and infrared light which we can't
see.
2
Light travels in waves, which are also called electromagnetic waves. Light waves can reflect,
refract, and be absorbed. Light reflects when it bounces back off of an object. Light reflects off
of a mirror. When light waves reflect, they bounce back from the surface at the same angle that
they hit the surface, in the same way that a billiard ball bounces back from the edge of a pool
table. Light refracts when it passes from one material to another and bends. If you put a pencil in
a glass of water, you can see where it seems to bend at the surface of the water. Light is
absorbed by most objects. A green object absorbs all of the colors except green; it reflects the
green color so green is the color that we see. What colors would a red apple absorb? How about a
lemon?
3
There are many optical devices that scientists use in their experiments. Sir Isaac Newton
used prisms to study the light spectrum. Galileo built and used telescopes to study the skies.
There are also many practical uses for optical devices. In addition to glasses and contacts,
cameras, binoculars, and projectors also use optical devices.
4
One of the main optical devices is the lens. A lens is a piece of glass or plastic with either one
or two curved surfaces. The curves change the direction of the light rays that pass through it. A
lens can either spread out the light rays or bring them closer together.
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A telescope uses lenses to allow us to see things so far away that we could not see them with
just our eyes. A basic telescope is a long tube with a large lens at one end that gathers light. At
the other end there is an eyepiece made of two small lenses, which magnifies the image that we
see. The Hubble space telescope, launched into space in 1990, detects not only visible light, but
also infrared and UV.
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A camera also uses lenses. When a camera's shutter opens, light from the scene being
photographed strikes a lens. Since the shutter is open for only a very short time, as little as
1/2000 second, this "freezes" the image. The light then passes on through the lens and forms an
upside-down image on the film at the back of the camera. When you focus a camera, what you are
actually doing is adjusting the distance between the lens and the film.
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Some newer uses of light include lasers and fiber optic cables. People who work in the field of
optics are also developing new and better cameras, telescopes, and other optical devices all of the
time. If you are someone who is interested in the mysteries of light, maybe you would like to find
out more about the field of optics.
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Copyright © 2007 edHelper
1. Optics is a branch of
A Chemistry
B Physics
C Geology
D Biology
2. Light travels in
A Waves
B Straight lines
C A yellow school bus
D Circles
3. Infrared and ultraviolet are part of the visible
light spectrum.
A True
B False
4. A lens has
A One curved surface
B Two curved surfaces
C Either a or b
D Two flat surfaces
5. Lenses are used in
A Eyeglasses
B Cameras
C Projectors
D All of the above
6. From the article you can infer that fiber
optic cables were invented
A After the telescope
B Before the telescope
7. From the article you can infer that UV stands
for
A Invisible
B A scientist's name
C A scientific formula
D Ultraviolet
8. How are a microscope and a telescope the
same? How are they different?
Draw the Electromagnetic Spectrum showing:
Gamma rays, X-rays, infrared, microwaves, radio waves, ultraviolet waves, and visible light.
Optics - The Study of Light Answer Key
1 Physics
2 Waves
3 False
4 Either a or b
5 All of the above
6 After the telescope
7
Ultraviolet
8 They are the same because they both use lenses to adjust what we see.
They are different bevause a telescope allows us to see things that are far
away, but a microscope allows us to see things that are very small.
Name:______________________________ Date:______________ Period:_______
What We See
By Sharon Fabian
When we look at something, say a waving flag, there are two things that affect what
we see, besides the flag itself. One thing is light waves; the other thing is our eyes.
1
You might remember that light waves are the part of the spectrum of electromagnetic waves
that is called visible light. Visible light comes in all of the colors of the rainbow, from red to violet.
All of these colors mixed together give us everyday white light.
2
Our eyes pick up light in much the same way that a camera does. Light enters our eyes through
the cornea, which is the clear covering over the front of the eye. The cornea bends, or refracts,
the light. Then the iris, the colorful part of the eye, opens or closes a little to let just enough light
through the pupil, which is an opening in the iris. The iris works like the shutter on a camera. The
light then passes through a lens behind the pupil, which focuses the light on the part of the eye
called the retina. The retina changes the light energy into electrical energy which carries the
message to the brain.
3
There are lots of great experiments that you can do to demonstrate facts about light. Light
experiments are interesting, and sometimes the results are surprising.
4
You can make a spinning top to demonstrate that white light is made up of all of the colors of
light. Cut out a circle of white cardboard and draw lines to divide it into wedges like a pizza. Color
the wedges in the colors of the rainbow, from red to violet. Poke a pencil through the center of
the circle and attach it with a little clay. Spin the top, and you will see the colors disappear. All
that you will see is white!
5
We can see objects because light is reflected off of them and into our eyes. Here is a
demonstration to show that it is really rays of light that are being reflected. You will need a
mirror, a flashlight, and two paper towel rolls. Stand the mirror up straight. Hold one paper towel
roll up to the mirror at an angle. Have a friend hold the other paper towel roll up to the mirror on
the other side at the same angle. The paper towel rolls should meet in the middle of the mirror.
Now shine a flashlight into the end of your paper towel roll. The light will reflect off of the
mirror, and you should be able to see the light shine out the end of the paper towel roll held by
your friend.
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You can also demonstrate a strange phenomenon called total reflection. Total reflection is
when light waves are reflected out in all directions so that you can no longer see the object at all.
Try this. Put a coin on a table. Now, set a jar on top of the coin. Pour water into the jar, and put
the lid on. No matter how much you try to see it through the water, the coin will seem to have
disappeared!
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Curved mirrors make reflections that have unusual sizes and shapes, because they reflect light
waves at changing angles. Look at your reflection in the side of a shiny metal cooking pot, or in a
spoon, and you'll get the idea. If you get the chance to look at your reflection in some fun house
mirrors, you will really see some unusual views of yourself! Don't worry though; you still look the
same to your friends. It's just a little magic, based on the science of light.
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Copyright © 2007 edHelper
What we see
1. Light waves contain
A Only plain white light
B No color
C Only black and white light
D All of the colors of the rainbow
3. Your eye works much like a
A Camera
B Mirror
C Top
D Rainbow
5. The paper towel roll experiment demonstrates
A That curved surfaces reflect light at different
angles
B That light is made up of many colors
C Total reflection
D That light waves reflect
7. The demonstration with the coin and the jar of
water shows
A Total reflection
B That light is made up of many colors
C That light waves reflect
D That curved surfaces reflect light at different
angles
2. The clear covering over the front of
your eye is called the
A Retina
B Iris
C Lens
D Cornea
4. The part of the eye that works like
the shutter of a camera is the
A Iris
B Retina
C Cornea
D Lens
6. The demonstration with the top
shows
A Total reflection
B That light waves reflect
C That curved surfaces reflect light
at different angles
D That light is made up of many colors
8. Fun house mirrors demonstrate
A That light waves reflect
B That curved surfaces reflect light at
different angles
C Total reflection
D That light is made up of many colors
9. Draw a diagram of an eye and a camera showing the similarities
What We See - Answer Key
1
2
3
4
5
6
7
8
All of the colors of the rainbow
Cornea
Camera
Iris
That light waves reflect
That light is made up of many colors
Total reflection
That curved surfaces reflect light at different angles
Name:_______________________________ Date:_____________ Period:______
Our Sense of Sight By Sharon Fabian
1
When you take a picture with a camera, you push the button, and the shutter opens just long enough to
let in enough light. The light, which is reflected from the people and things that you are taking a picture of,
focuses on the film in the camera where it leaves a picture, or image. Our eyes work much like a camera.
They take in light and focus it on a particular spot to create an image.
2
Light enters our eye through the pupil, the black part of the eye. Surrounding the pupil is the colored
part called the iris. The pupil is actually an opening especially for collecting light, and the iris is a set of
muscles that adjust the opening to let in just the right amount of light. That is why your pupil gets larger in
a dark room and smaller in bright sunlight. The iris is adjusting it for the amount of light. Covering the iris
and the pupil is a tough, clear covering called the cornea.
3
After light passes through the pupil, it next passes through the lens, which focuses the image some
more. Muscles surrounding the lens stretch or relax to make it focus just right. The lens focuses the image
onto the retina, which covers most of the back part of the eye. At this point the image is upside down! The
retina is covered with tiny parts called photoreceptors, which change the light energy into electrical energy.
The electrical signals are picked up by the optic nerve at the back of the eye. The optic nerve is actually
made up of millions of very tiny bundles of nerves, which send the message (or the picture, or the image,
whatever you would like to call it) to the brain.
4
The eye also contains a material called vitreous gel. It's a clear jelly-like material inside the eye. Its
purpose is to help the eye keep its round shape.
5
With our sense of sight we can see not only shapes, sizes, and colors, but we can also see whether
something is far away or near, and we can tell if something is moving towards us or away from us. If you're
interested in this part of the sense of sight, try researching the subject of binocular vision, or 3-D vision.
6
If you have trouble seeing and go to see the school nurse or an eye doctor, they will check your visual
acuity. Visual acuity means how well your eyes see, and it is often checked using one of those eye charts with
the letters printed in different sizes. You may have heard of people having 20/20 vision. 20/20 vision means
that you can see the letters on the eye chart from 20 feet away as well as any person with normal vision can
see them. 20/20 vision does not mean perfect vision; some people have better than 20/20 vision. If you have
20/15 vision, that means that you can see as well from 20 feet away as the average person can see from 15
feet. A few people even have 20/10 vision!
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Other people have problems with their vision. Some people cannot see far away things very well. Some
people have trouble seeing things that are very close and small, like words printed on a page. Some people
can only see light, but cannot recognize objects or people. Some people can see only in the daylight.
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Vision problems can cause all kinds of every day difficulties, from difficulty reading to trouble seeing
the blackboard. More serious vision problems make it hard for a person to move around and may limit the
type of work that a person can do. So people with vision problems often use something to aid their vision.
You probably know many people who wear glasses or contact lenses. Some people have surgery to correct eye
problems. People with very limited vision may use a cane or another device to help them travel safely. Guide
dogs also help people who cannot see well to continue to travel independently.
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Vision is just one of our five senses, and people who do not have good vision seem to make up for it by
developing their other senses especially well. For those of us who can see books, toys, landscapes, and our
friend's faces, the sense of sight is definitely something to be thankful for.
Copyright © 2007 edHelper
1. The pupil is
2. The optic nerve is
The part that sends a message to the brain
The colored part of the eye
The opening that lets light in
The part that sends a message to the brain
A group of muscles
A group of muscles
The colored part of the eye
The opening that lets light in
3. The iris is (choose two)
4. Which part of the eye is like the shutter on a
camera?
The opening that lets light in
Optic nerve
The part that sends a message to the brain
Iris
The colored part of the eye
Retina
A group of muscles
Pupil
5. Which part of the eye is like the film in a
camera?
Retina
Iris
Pupil
Optic nerve
6. 20/20 means perfect vision.
True
False
7. Guide dogs help people with limited vision to
travel independently.
True
False
8. Vision is just one of our five senses. Can you
name the other four?
Our Sense of Sight - Answer Key
1
The opening that lets light in
2 The part that sends a message to the brain
4 Pupil
5
Retina
6 False
7 True
8 hearing, touch, taste, and smell