Download Elements of Physics Light: Optics and Electricity

Elements of Physics
Light: Optics and Electricity
Producer/Director
Wendy Loten
Animation and Graphics
Wesley Cudlip
Educational Consultants
Daniel Coté, MSc
Dr. David Harrison
University of Toronto
Physics Department
Editor
Gina Binetti
Writer/Researcher
Bill Freeman, Ph.D.
Teacher’s Guide
Bill Freeman, Ph.D.
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Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . .1
Links to Curriculum Standards . . . . . . . . . .1
Student Objectives . . . . . . . . . . . . . . . . . . .1
Summary of the Program . . . . . . . . . . . . . .2
Pre-Test and Post-Test . . . . . . . . . . . . . . . . .3
Teacher Preparation . . . . . . . . . . . . . . . . . .4
Student Preparation . . . . . . . . . . . . . . . . . . .5
Description of Blackline Masters . . . . . . . .5
Answer Key . . . . . . . . . . . . . . . . . . . . . . . .6
Discussion Questions . . . . . . . . . . . . . . . . .9
Extended Learning Activities . . . . . . . . . . .11
Reference List . . . . . . . . . . . . . . . . . . . . . . .12
Script of Narration . . . . . . . . . . . . . . . . . . .13
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Elements of Physics Series
Light: Optics and Electricity
Grades 9 to 12
Viewing Time: 20 minutes
INTRODUCTION
Light: Optics and Electricity is part of the Elements of
Physics Series, a six-part series of programs designed to help
students understand fundamental concepts of physics.The
attractive images and engaging narration of the programs have
been designed by educators and filmmakers to help students
understand the sometimes complicated and obscure scientific
explanations of our physical world.
The study of light was difficult for physicists because of its
incredible speed, but once a theoretical understanding was
achieved it led to our development and use of electricity and a
whole range of electronic devices. This program focuses on the
way that physicists understand and explain light, optics, and
electricity and provides a comprehensive introduction to this
fascinating area of science.
LINKS TO CURRICULUM STANDARDS
Elements of Physics Series, is based on the "National Science
Educational Standards" for "Physical Science," grades 9-12,
(Content Standard B).
STUDENT OBJECTIVES
After viewing the program and participating in the various follow up activities, students should be able to do the following:
• Describe how we see objects either by light reflected from
their surfaces or because they are luminescent.
• Define the angle of incidence and the angle of reflection in
mirrors.
• Explain how convex mirrors cause light rays to diverge and
concave mirrors cause the rays to converge.
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• Explain what causes refraction and how it is the basis of a
wide variety of optical devices from telescopes to magnifying
glasses and the lenses in our eyes.
• Describe the principles of concave and convex lenses and how
they can correct faults in eyes.
• Describe how light breaks into the colors of the spectrum
when it passes through a prism.
• Give a general explanation of the electromagnetic theory of
light.
• Describe the electromagnetic spectrum and explain how wave
frequencies determine the nature of the wave.
• Explain why physicists think the speed of light is one of the
fundamentals of the universe.
• Define the importance of the light-year as a unit of measurement in the study of the universe.
• Explain the relationship between the electromagnetic spectrum and technologies such as radio, television, cellular telephones, telecommunications satellites, microwave ovens, radar,
and X-rays.
• Illustrate how electricity is generated and transported.
SUMMARY OF THE PROGRAM
The study of light has long been a fascination of physicists, but
it has only been in the last 150 years that an adequate understanding has been achieved.
It was in the area of optics that the first breakthroughs were
made. We see objects because light is reflected off their surfaces to our eyes. Light bulbs, on the other hand, are luminescent; they generate their own light by electricity.
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Physicists who studied mirrors learned that the shape of the
mirror shaped the image that was reflected from its surface.
Refraction is an optical distortion of the image caused by light
traveling at different speeds in different mediums. Refraction is
the basis of optical devises such as magnifying glasses, eyeglasses, and even the lenses in our eyes.
It was not until the middle of the 19th century that physicists
gained significant insights into the nature of light. James Clerk
Maxwell showed that electricity and magnetism were linked in
one of the basic forces of nature called the electromagnetic
spectrum. The spectrum ranges from gamma rays, with the
highest wave frequency, to radio waves, the slowest. Visible
light is a narrow band in the middle of the electromagnetic
spectrum. Einstein, developing on the work of Maxwell,
demonstrated that the speed of light was one of the fundamentals of the universe.
In the last century and a half, scientists and inventors have
learned to harness the electromagnetic spectrum for our own
use. Radio and television are broadcast using radio waves;
telecommunications satellites pass signals from the surface of
the Earth to the satellite and back to Earth again; microwaves
are used in radar, cell phones, and ovens; and X-rays and
infrared rays use waves of higher frequency.
Electricity is by far the most important application of our
understanding of electromagnetism. Its development has truly
revolutionized our way of life.
PRE-TEST AND POST-TEST
Blackline Master #1, Pre-Test, is an assessment tool intended
to gauge student comprehension prior to viewing the program.
Remind your students that these are key concepts upon which
they should focus while watching the program.
Blackline Master #7, Post-Test, can be compared to the results
of the Pre-Test to determine the changes in student comprehension after participation in the activities and viewing the program.
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TEACHER PREPARATION
Before presenting this program to your students, we suggest
that you preview the program and review this guide and accompanying Blackline Master activities in order to familiarize yourself with the content. Feel free to duplicate any of the Blackline
Masters and distribute them to your students.
As you review the materials presented in this guide, you may
find it necessary to make some changes, additions, or deletions
to meet the specific needs of your class. We encourage you to
do this. Only by tailoring this program to your class will your
students obtain the maximum instructional benefits afforded by
the materials.
We suggest that you first show the program in its entirety to
your students. This is an introduction to the complex subject of
light, and at this stage it is helpful that students gain an
overview of the concepts and material in the program. A number of lesson activities will grow out of the content of the program and, therefore, the presentation should be a common
experience for all students.
After the introduction the program is divided into chapters with
the following titles:.
• Optics
• Refraction
• What is Light?
• The Speed of Light
• Putting the Electromagnetic Spectrum to Use
• Electricity
These chapters vary in length from three to five minutes. After
the students have seen the entire program, lessons could be
designed around these different chapters. A chapter could be
shown at the beginning of the class, and the balance of the class
time, and subsequent classes, could be spent examining the subject matter in the program in greater depth.
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STUDENT PREPARATION
It is important that students work through the material and
familiarize themselves with the vocabulary, concepts, and theories that scientists use to understand this field.
If the students have a textbook that they are following, assign
the relevant reading before the lesson. As students work
through the material, they will encounter a number of unfamiliar words and concepts. Most of these words are highlighted in
the program. An additional list of words is provided in
Blackline Masters #2a-c, Vocabulary Definitions and
Activities.
The program concludes with a 10-question Video Quiz that
may be used to gauge students' comprehension immediately
after the presentation of the program. Blackline Master #6,
Video Quiz, is a printed copy of the questions, which may be
reproduced and distributed to the students. The answers to the
questions appear in the answer key of this Teacher's Guide.
DESCRIPTION OF BLACKLINE MASTERS
Blackline Master #1, Pre-Test, should be given to students
before viewing the program. When these answers are compared
to the Post-Test results, it will help you gauge student progress.
Blackline Master #2a, Vocabulary Definitions, will introduce
students to unfamiliar words and concepts used in this program.
Blackline Master #2b, Use the Right Word, and Blackline
Master #2c, Word Match, are activities designed to help reinforce key concepts and vocabulary.
Blackline Master #3, Connected/Not Connected, will help
students identify their knowledge of key vocabulary terms and
the context in which they are used.
Blackline Master #4, Crossword Puzzle
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Blackline Master #5, Creative Writing Story Ideas, will
allow students to think creatively while incorporating scientific
principles and vocabulary covered in this program.
Blackline Master #6, Video Quiz, is a printed version of the
Video Quiz that appears at the end of the program.
Blackline Master #7, Post-Test, may be used to evaluate student progress after completing this lesson.
ANSWER KEY
Blackline Master #1, Pre-Test
1. false
2. true
3. true
4. false
5. false
6. false
7. true
8. true
9. false
10. false
Blackline Master #2b, Use the Right Word
1. optics
2. refraction
3. luminescent
4. light-year
5. convex
6. electromagnetism
7. insulators
8. reflecting
9. X-rays
10. electricity
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Blackline Master #2c, Word Match
concave
a lens or mirror curved inward
convex
a lens or mirror curved outward
electromagnetism
waves of electricity and magnetism
focus
point at which light rays come together
light-year
distance light travels in a year
luminescent
objects that radiate light
prism
disperses light into colors of the spectrum
radio waves
electromagnetic waves used in telecommunication
reflection
image thrown back by a barrier
visible light
electromagnetic waves that allow vision
Blackline Master #3, Connected/Not Connected
1. incidence
reflection
2. convex
concave
3. refraction
medium
4. mirrors
lenses
5. prisms
visible
6. radio
gamma
7. electric
luminescence
8. light-year
space
9. radar
cellular phones
10. conductors
insulators
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Blackline Master #4, Crossword Puzzle
1
3
4
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S
U
A
T
O
R
5
E
9
L
L
F
I
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G
A
H
C
O
N
D
U
C
T
6
7
O
F
Q
L
M
U
E
I
E
C
C
O
N
O
Y
W
N
C
N
R
F
I
O
2
S
E
T
C
U
E
C
O
C
R
R
11
O
A
V
E
V
E
8
X
10
R
T
A
D
I
A
O
Y
N
O
S
V
12
O
13
P
E
R
I
S
M
S
I
B
L
T
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V
I
E
C
S
Blackline Master #6, Video Quiz
1. true
2. reflection
3. false
4. refraction
5. true
6. true
7. frequencies
8. false
9. true
10. insulators
Blackline Master #7, Post-Test
1. focus
2. electromagnetic
3. microwaves
4. light-year
5. false: Depending on the shape of the lens, they can either
converge or diverge light.
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6. false: Telecommunications signals are carried by electromagnetic waves. These signals are usually radio or microwaves. Standard telephones operate with electricity.
7. true
8. false: Both are electromagnetic waves, but gamma rays have
the fastest wave frequencies in the electromagnetic spectrum
while radio waves are the slowest.
9. false: Conductors are materials that enhance the flow of electricity while insulators stop or inhibit the flow.
10. Light travels at different speeds in different mediums. For
example, because air is less dense than water, light travels faster
in air than water. This creates a distorted image and the object
appears bent or broken at the point where the two mediums
meet. This is called refraction and is the basis of all lens technology.
11. When an electron changes direction the oscillations generate electromagnetic waves of energy that are propagated at the
speed of light. These electromagnetic waves range from gamma
rays, with very high frequencies, to radio waves that have much
lower frequencies. Visible light is a narrow band, containing all
of the colors, in the middle of the electromagnetic spectrum.
12. Einstein said that matter and energy could not travel faster
than the speed of light. If something traveled at those speeds it
would literally arrive before it left and that is impossible. The
only thing that is able to travel at the speed of light is electromagnetic waves in the vacuum of space.
DISCUSSION QUESTIONS
1. What is the similarity between the stars, the sun, molten
metal, and a light bulb?
They are all luminescent. They generate and radiate electromagnetic waves, which we can see as a form of light. Objects
such as buildings, trees, people, the moon, and planets we see
as light reflected off their surfaces.
2. Are there different types of telescopes?
Yes, there are a great variety of telescopes. In the 16th century,
glass-manufacturing techniques greatly improved. Galileo
developed a telescope using glass lenses to look at the stars.
Others improved on this technique but they found that larger
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and larger lenses were needed to increase the magnification.
Newton solved this problem by using mirrors to focus the
image and since his day most telescopes are based on this principle. Today there are even a greater variety of telescopes.
Radio telescopes study radio waves from the stars and infrared
telescopes have been built. One of the most important recent
developments in astronomy came when the Hubble Telescope
was placed in orbit. For the first time a telescope was raised
above the distorting effects of the Earth's atmosphere and it has
produced a spectacular series of images of the heavens. There
are now plans to place a telescope in deep space outside the
orbit of the Earth altogether.
3. What is the relationship between science and the technical
instruments that help us study nature?
Our ability to provide scientific explanations has always been
limited by our ability to observe. Astronomy is one of the best
examples of this. Our understanding of the universe, and our
explanations of how it was formed and developed, has been
limited by the telescopes and other instruments we have to
observe the heavens. Scientific theory and empirical observation are both essential to the development of science.
4. The television program "Star Trek" suggests that the
"Starship Enterprise" can travel faster that the speed of light in
what they call warp-speed. Is that possible?
Not according to Einstein and the best physicists of our day.
The theory of relativity concludes that at the speed of light,
matter would disintegrate into sub-atomic particles, and if anything traveled faster than the speed of light it would arrive
before it left. "Star Trek" is truly in the realm of science fiction.
5. Will the speed of light be a limitation to space travel?
Yes. It is possible to imagine that we can travel to planets within our solar system, but even here the distances are enormous
and the time to travel to distant stars and planets would take
years. The distances beyond our solar system are almost impossible to imagine. Alpha Centuri, our closest star beyond the sun,
is 4.3 light-years away, and the center of the Milky Way Galaxy
is estimated to be 27,000 light-years away. Travel to any place
beyond our solar system would take centuries. But even if we
10
do not travel to distant stars, astronomy has shown we can learn
a great deal about the universe from here on Earth.
EXTENDED LEARNING ACTIVITIES
The following activities and projects might prove useful to students studying the subject of light, optics and electricity.
1. Set up a flat mirror at an angle to the point of observation.
Calculate the angle of incidence and the angle of reflection.
Write a report describing your experiment, how you preformed
your calculations, and your conclusions.
2. Study convex and concave lenses. Draw diagrams showing
what happens to the light rays as they go through each lens and
write captions to the diagrams explaining the phenomena.
3. Draw diagrams showing how optometrists use lenses to correct the vision of near-sighted and far-sighted patients. Explain
some of the other vision problems that people experience and
how they can be corrected with lenses.
4. Draw a diagram of the electromagnetic spectrum and explain
why visible light is only a small part of the phenomenon of
light.
5. Calculate the distance in miles or kilometers between the
solar system of the sun and three of our nearest stars. If an
astronaut can travel at half the speed of light, how long will it
take him or her to arrive in the vicinity of these stars? What limitation does this place on space travel? Are there any solutions?
6. Research two different types of telescopes. Describe how
they work and explain the advantages and disadvantages of
each of them.
7. Visit a planetarium or observatory that is open to the public.
Report on some interesting aspect of the presentation such as
space travel, distances of the stars, or the origins of the universe.
11
8. Visit a television station and describe the technology of how
the program is transmitted and then received into your home.
9. Current affairs, television, and radio programs often feature
a host talking to a journalist on the other side of the world about
a fast breaking story. The host will ask a question and there is
a noticeable pause before the journalist replies. What is the reason for that pause? Is there any way that it can be avoided?
Report on your findings and conclusions.
10. Research the way the electricity received in your community is generated. Write a report showing how your city, town, or
countryside could develop an electric generating system that is
less polluting than the one in use. What are the advantages and
disadvantages of the system that you have designed?
REFERENCE LIST
There are many excellent books and websites dealing with
light, optics and electricity that are appropriate for students and
available in libraries. The following is a short list.
Books:
Physics, A Practical Approach, Hirsch, Alan J., Second
Edition, New York: John Wiley and Sons, 1991.
Physics, Huber-Schaim, Uri, John H. Dodge, James A. Walter,
Fifth Edition, Lexington, Mass.: D.C. Heath and Co., 1981.
Basic Physics: A Self-Teaching Guide, Kuhn, Karl F., Second
Edition, New York: John Wiley and Sons Inc., 1996.
Physics, Principles and Problems, Zitzewitz, Paul W., New
York: Glenco-McGraw-Hill, 1999.
Internet Sites:
http://www.aapt.org
This is the website of the American Association of Physics
Teachers, an organization of physics high school teachers.
They also publish a magazine called The Physics Teacher.
12
http://enrich.sdsc.edu/SE/opticsintro.html
This site is prepared by the Science Enrichment Program and
designed for students. It has detailed information on various
optical devises and excellent diagrams.
http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum
html
This is one of the best sites that describes the electromagnetic
spectrum. The diagrams are easy to understand and the text is
clear.
www.colorado.edu/physics/2000/waves_particles/wpwaves5.ht
ml
This excellent website was prepared by the University of
Colorado. It has detailed information about quantum physics
and is particularly good on electromagnetism.
\
SCRIPT OF NARRATION
The study of light has been central to physics since the days of
the Ancient Greeks, but despite the remarkable strides in our
understanding there are still debates as to its true nature.
We are going to review the way physicists understand light by
looking at optics, electromagnetism, and the speed of light. The
program will illustrate the way these theoretical understandings
have led to the development of our use of electricity and other
electronic devices.
OPTICS
We see objects either because light is reflected off their surfaces
to our eyes or because the objects themselves are luminescent.
We can see the moon, for example, because light from the sun
is reflected off its surface. Amusement rides, flowers, and birds
- we see all of these objects because light is reflected off their
surfaces to our eyes. But a neon sign, or a light bulb is luminescent; they generate their own light by electricity.
In nature, we often see examples of light being reflected, as on
the surface of water, or polished surfaces. Mirrors offered sci13
entists a way to study reflection and early experiments showed
that light travels in a straight line and bounces off mirrors in
predictable ways.
Physicists discovered that the angle at which the light ray
strikes the surface, called the angle of incidence, is equal to the
angle at which it bounces off, called the angle of reflection.
Moving the mirror changes which rays are reflected into our
field of view. By moving the mirror we can see what is behind
us without turning our heads!
Changing the shape of the mirror from flat to convex causes the
reflected light rays to diverge. On the other hand, a concave
mirror causes the light rays to converge and intersect at a point
called the focus. In both of these cases, light is obeying the laws
of reflection. The light travels in a straight line but the shape of
the mirror distorts the reflected image.
REFRACTION
Another phenomenon of light is called refraction. This pencil
appears broken at the water line. The reason this happens is
because light travels at different speeds in different mediums.
Air is a less dense medium than water and light waves travel
faster through air than through water.
When the light meets the boundary of the new medium at an
angle, the light wave is bent before continuing in a straight line.
This creates the distorted image. Both reflection and refraction
involve a change in direction of a wave, but only refraction
involves a change in medium.
The refraction of light is the basis of optical devices such as
eyeglasses, magnifying glasses, binoculars and even the lenses
in our own eyes. When light enters the new medium of the lens,
its speed is slowed and the light ray is refracted, when it enters
and also when it leaves. Some lenses are convex, and cause the
light rays to converge; others are concave and cause the light to
diverge.
The refracted light rays can be focused by the lens to form an
image. In our eyes, muscles can change the shape of the lens
14
and focus the image clearly on the optic nerve at the back of the
eye. Sometimes the shape of the lenses of our eyes doesn't focus
the image clearly and our vision is blurred. Specially shaped
glasses correct this fault.
By using different combinations of lenses and mirrors to form
images, we can make all sorts of optical devices from cameras
to microscopes. The early telescopes were all built with lenses
but they were limited by the physical size of the lens. All of
the large optical telescopes in use today are reflecting telescopes that use mirrors to focus the light.
One of the most interesting devices that refracts light is a prism,
an angled piece of glass. Notice how the white light is broken
into the spectrum of the rainbow: seven colors: red, orange, yellow, green, blue, indigo, and violet. Why does this happen?
The reason was only discovered when scientists were able to
understand the complex nature of light.
WHAT IS LIGHT?
What is light? It took until the middle of the nineteenth century before some of the basic questions were answered.
In 1873, James Clerk Maxwell, a British physicist, developed
equations based on the link between electric fields and magnetic fields. The oscillations, or movements back and forth of electric charges within these fields generate electromagnetic waves
of energy. Maxwell's calculations of the velocity of these waves
matched the speed of light and led him to predict that light is a
form of energy that travels as an electromagnetic wave.
The electromagnetic spectrum consists of bands of waves that
have different frequencies. From the highest frequency waves
with the highest energy to the lowest frequency with the lowest
energy, the waves range from gamma rays, X-rays, ultra violet
rays, visible light, infra-red rays, micro waves to radio waves.
What we call light - or visible light - is only a narrow band in
the electromagnetic spectrum.
Included in that band are all of the colors. Each of the colors has
a different wavelength. The longest wavelength is the color red
15
and the shortest, violet. Because of the different wavelengths,
the light rays bend at a different rate when they go through the
prism and create the rainbow.
The tremendous energy coming from the sun is the greatest
source of electromagnetic radiation in our solar system but we
can also generate light ourselves here on Earth. Fire is a source
of electromagnetic energy. The chemical reaction of burning
releases electromagnetic radiation that we see as light. Electric
lights become luminous when electricity flows through the filament in the bulb, causing it to heat and glow when it is brought
to a high enough temperature.
THE SPEED OF LIGHT
Light travels so fast that it was once thought that it was instantaneous. But in 1673, the speed of light was first successfully
measured after many observations of the orbiting moon of
Jupiter. Light, it was found, took time to travel across space.
In the early 1900s, while working on different aspects of the
theory of relativity, Albert Einstein concluded that the speed of
light was one of the fundamentals of the universe. Einstein said
that matter and energy could not travel faster than the speed of
light because as matter accelerates, its mass increases and more
energy is required to accelerate it further. As it approaches the
speed of light, the energy requirements become infinite. This
makes it impossible for any mass to travel faster than light.
After research over many years it has been determined that the
speed of light through the vacuum of space is 299,792.458 kilometers per second, or 186,282.4 miles per second. If you could
travel at the speed of light, you could go from London, England
to Los Angeles, California in less than one-twentieth of a second! Imagine how far light travels in the vacuum of space in
one year. This is called a light-year, and is now used as the
world's standard for measuring distance because it never varies.
Astronomers use the measurement of the light-year to calculate
the vast distances between objects in space. Our solar system is
in the Milky Way Galaxy, which is made up of about 100 billion stars. This disk-shaped galaxy is about 100,000 light16
years across and we live about 27,000 light years from the center. Astronomers believe there are billions of galaxies, some as
far away as 10 billion light-years.
When we look at the night sky we are seeing ancient light that
has taken so long to reach us, the stars that produced it may no
longer exist.
PUTTING THE ELECTROMAGNETIC SPECTRUM TO USE
In the last 150 years, scientists and inventors have built on the
understanding of the differing wavelengths and frequencies of
the electromagnetic spectrum to develop a dizzying array of
technologies that have benefited all of us.
Radio waves have the lowest frequency in the electromagnetic
spectrum. When a radio program is broadcast an antenna sends
out radio waves at a certain frequency - or number of waves per
second. Every radio station has its own frequency. When we
tune in a station what we are doing is adjusting our radio to the
same frequency of the radio wave broadcast from the station's
antenna. When they are both on the same frequency our radio
receives the signal from the station and transforms it into sound
waves, which we can hear. Many radio waves can be broadcast
at the same time. As long as they are transmitted on different
frequencies, none of them will interfere with the others.
Television works in much the same way but the frequencies are
higher in the electromagnetic spectrum. An electric signal carrying information about the image arrives at the back of the television tube. Those signals send electrons to the front of the
tube creating dots of light on the screen. Those dots are quickly assembled as an image, which changes so quickly it appears
to move and provide action.
The curvature of the Earth limits the reception range of
telecommunication signals since electromagnetic waves usually travel in a straight line. In recent years, satellites have been
placed in orbit high above Earth to get around this problem.
Signals are sent from Earth to the satellite and back to Earth
again. In this way signals can be sent all over the globe.
17
Increasingly electromagnetic waves with higher frequencies are
being used. The signals in cellular phones and telecommunication transmitters are microwaves. The same type of wave is
used in microwave ovens.
Radar is another use. It was developed in the Second World War
to detect incoming enemy airplanes. Microwaves are sent out
from a tower. The beams bounce off incoming aircraft and
some of the signal returns to the tower. Instruments read this
signal to give the location of the aircraft, its speed and direction.
Today, radar is an essential tool for defense and civil aviation.
Infrared rays have been adapted to help people see in the dark.
Ultraviolet is used in florescent lighting. X-rays are used for
dental and medical applications because their short wavelengths can penetrate soft tissue and show bones.
The difficulty in using the waves that are higher in the spectrum
is that they can be dangerous to humans. Overexposure to Xrays, for example, can lead to serious medical problems. But
the more that is learned about electromagnetism the more applications are found.
ELECTRICITY
By far the most useful application of electromagnetism has
been the development of electricity.
The key to understanding electricity is in atoms, the basis of all
matter. Atoms consist of negatively charged electrons that orbit
around a nucleus made up of positively charged protons and
neutral neutrons. It is the movement of the electrons that generate changes in electromagnetic fields of energy that is electric
power.
In 1831, Michael Faraday, a British scientist, demonstrated that
electricity could be generated when a magnet was moved inside
a coil of wire. Moving the magnet one way in the coil causes
the electrons in the wire to flow in one direction. When the
magnet moves back again, the electrons reverse and flow in the
opposite direction. What is created in this process is an alternating electric current. The application of this research led to
the commercial development of electricity.
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But how is the electricity transported? Opposite electrical
charges attract and like electrical charges repel each other.
Electrons have a negative charge and they can jump from atom
to atom and molecule to molecule. When there is a build up of
electrons they will be attracted to positively charged protons.
When a negative charge has built up in one location and a positive charge in another location, and if they are connected with
a good conductor, the negatively charged electrons will flow
along the conductor to the positive charge. There are some
materials that are good conductors of electrons like metals,
water and the human body.
Insulators are the opposite of conductors; they are materials that
inhibit the flow of electrons. Examples include rubber, plastics,
paper and glass. The copper of an electric wire is an excellent
conductor. It is covered with a plastic coating, which is a good
insulator. The conductor allows the electrons to flow along it
but the insulator stops the electric power from leaking out.
Understanding of these basic principles lead to the rapid development in the technology of electricity, which has transformed
our lives. By 1873, it was shown how electric power could be
transmitted through wires, and in 1879, Thomas Edison, the
American inventor, developed his incandescent light bulb. By
1900, electric power was being widely used in North America
and Europe and today electric power is used in virtually every
part of the globe as the source of energy for a wide variety of
uses.
Most electricity used today is still generated by turning a magnet within a coil of wire. This takes a tremendous amount of
mechanical energy that can be provided in a number of different ways. The waterpower of Niagara Falls was one of the earliest sources of power in North America. Windmills or steam
driven turbines heated by nuclear power or fossil fuel such as
coal and natural gas can also generate electric power.
Today we use electricity to drive complicated machinery in factories, various types of vehicles and as a source of power to run
a wide range of household appliances. The benefits that we
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have received from the efforts of physicists in unlocking the
mysteries of light, electromagnetism, and electricity have been
truly amazing.
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1
Name ____________________
ELEMENTS OF PHYSICS
LIGHT: OPTICS AND ELECTRICITY
Pre-Test
Directions: This will help you discover what you know about the subject of light optics and
electricity before you begin this lesson. Answer the following true or false.
1. We always see objects because light is reflected off their surfaces.
T_______ F_______.
2. A light bulb is luminescent because it radiates light.
T_______ F_______.
3. The angle of incidence of a mirror is equal to the angle of reflection.
T_______ F_______.
4. Refraction is a reflected image.
T_______ F_______.
5. Convex mirrors cause light rays to converge.
T_______ F_______.
6. The electromagnetic spectrum only contains visible light.
T_______ F_______.
7. Physicists believe matter cannot travel faster than the speed of light.
T_______ F_______.
8. A light-year is the distance light can travel in a vacuum in a year.
T_______ F_______.
9. Radio waves run microwave ovens.
T_______ F_______.
10. Insulators conduct electricity.
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T_______ F_______.
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2a
Name ____________________
ELEMENTS OF PHYSICS
LIGHT: OPTICS AND ELECTRICITY
Vocabulary Definitions
The following words and terms used in the program may be unfamiliar to you. Try to listen for these terms
while viewing the program, pay close attention so you can later include them in your scientific descriptions,
observations, and creative writing assignment activities.
angle of incidence - the angle at which the image strikes luminescent - objects that radiate light.
a mirror.
Maxwell, James Clerk - British physicist, 1831 - 1879.
angle of reflection - the angle at which the image is
reflected off a mirror.
medium - an intervening substance that allows energy to
pass such as air, water, or solids.
Aristotle - ancient Greek philosopher, 384 - 322 BC.
microwaves - electromagnetic waves used in cellular
concave - a lens or mirror curved inward.
phones, radar, and ovens.
conductor - conducts electricity.
convex - a lens or mirror curved outward.
Edison, Thomas - American inventor, 1847 - 1931.
neutrons - part of the nucleus of atoms with no electrical charge.
optics - branch of physics dealing with light and vision.
photons - sub-atomic particles of energy and matter
Einstein, Albert - German-American physicist, 1879 - propagated by electromagnetic waves.
1955.
prism - a glass or crystal with equal sides that can diselectromagnetic spectrum - includes all of the electro- perse light into the colors of the spectrum.
magnetic waves with different wavelengths and frequencies.
protons - positively charged part of the nucleus of
atoms.
electromagnetism - waves of electricity and magnetism,
often called light.
radio waves - electromagnetic waves used in telecommunications.
electrons - negatively charged particles that orbit the
nucleus of atoms.
reflecting telescope - a telescope where the image is
enlarged by mirrors.
Faraday, Michael - English chemist and physicist, 1791
- 1867.
reflection - an image thrown back by a barrier like a mirror.
focus - point at which light rays come together.
refraction - because light travels in different speeds in
frequency - number of waves in a given unit of time.
different mediums, objects appear broken or refracted,
where the two mediums meet. Refraction is the basis of
gamma rays - the fastest waves in the electromagnetic lens technology.
spectrum.
ultra violet rays - electromagnetic waves used for
infrared rays - electromagnetic waves used for heating florescent lighting and heating.
and seeing in the dark.
visible light - electromagnetic waves in the middle
insulators - inhibit the flow of electricity.
of the spectrum that give visible light.
light-year - the distance that light travels in a vacuum in X-rays - electromagnetic waves used in dental and
one year.
medical imaging.
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2b
Name ____________________
ELEMENTS OF PHYSICS
LIGHT: OPTICS AND ELECTRICITY
Use the Right Word
Directions: Find the right word from the physics vocabulary list that completes the following sentences.
1. The branch of physics dealing with light and vision is called ____________.
2. ____________ is the basis of lens technology.
3. Objects that radiate light are ____________.
4. A ____________ is the distance that light travels in a vacuum in one year.
5. A lens or mirror curved outward is called ____________.
6. Waves of electricity and magnetism are called ____________.
7. ____________ inhibit the flow of electricity.
8. A ____________ telescope enlarges the image with mirrors.
9. The electromagnetic waves used in medical imaging are called ____________.
10. ____________ is usually generated by rotating a magnet in a coil of wire.
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2c
Name ____________________
ELEMENTS OF PHYSICS
LIGHT: OPTICS AND ELECTRICITY
Word Match
Directions: Connect the word with the proper definition.
concave
distance light travels in a year
convex
objects that radiate light
electromagnetism
image thrown back by a barrier
focus
a lens or mirror curved inward
light-year
electromagnetic waves used in telecommunication
luminescent
electromagnetic waves that allow vision
prism
waves of electricity and magnetism
radio waves
point at which light rays come together
reflection
disperses light into colors of the spectrum
visible light
a lens or mirror curved outward
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3
Name ____________________
ELEMENTS OF PHYSICS
LIGHT: OPTICS AND ELECTRICITY
Connected/Not Connected
Directions: Place the following words in the proper sentences.
cellular phones
concave
conductors
convex
electric
gamma
incidence
insulators
lenses
light-year
luminescence
medium
mirrors
prisms
radar
radio
reflection
refraction
space
visible
1. The angle of ____________ is connected to the angle of ____________ because both angles are exactly
the same.
2. ____________ lenses are NOT connected to ____________ lenses because one causes light rays to converge
and the other causes them to diverge.
3. ____________ is connected to ____________ because light travels faster through some substances than others
making the image appear bent or broken.
4. ____________ are NOT connected to ____________ because one reflects light and the other causes light
to be refracted.
5. ____________ are connected to ____________ light because these angled pieces of glass or crystals break
light into a spectrum of seven colors.
6. ____________ waves are NOT connected to ____________ rays because one is the slowest wave in the
electromagnetic spectrum and the other is the fastest.
7. ____________ lights are connected to ____________ because they radiate light.
8. The ____________ is NOT connected to ____________ travel because the incredible distances in space that it
measures will make this form of travel very difficult.
9. ____________ and ____________ are connected because both use microwaves to transmit their signal.
10. ____________ of electricity are NOT connected to ____________ of electricity because one inhibits the
flow of electricity and the other enhances it.
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4
Name ____________________
ELEMENTS OF PHYSICS
LIGHT: OPTICS AND ELECTRICITY
Crossword Puzzle
1
2
3
4
5
6
7
9
8
10
11
12
13
14
Across
1. point at which waves come together
3. material that inhibits the flow of electricity
7. lens or mirror curved outward
9. material that enhances the flow of electricity
10. waves used in television
11. lens or mirror curved inward
13. glass that disperses light into the colors of the spectrum
14. the _________ light of electromagnetic spectrum lets us see
Down
1. number of waves in a unit of time
2. thrown back by a barrier
4. the image appears bent where two mediums meet
5. electromagnetic waves
6. electromagnetic waves used in cellular phones
8. electromagnetic waves used in medical imaging
12. dealing with light and vision
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5
Name ____________________
ELEMENTS OF PHYSICS
LIGHT: OPTICS AND ELECTRICITY
Creative Writing Story Ideas
Directions: Choose from one of the ideas listed below and write a story or dramatization. Include plot lines
that follow scientific principles and key vocabulary terms.
1. You are shipwrecked on a desert island with only a mirror and a convex lens as tools. Tell the story of how you
use these instruments for your survival and rescue.
2. Jack Hoggins, genius inventor, works in an electronics store filled with computer games and electronic gadgets.
The storeowner asks Jack to design a security system using some of the stuff in the store. Two days after the system is installed, May Squires arrives. Is she intent on plundering the till or testing the system? A little humor
might be appropriate as you tell the story of the events of that fateful afternoon.
3. Every evening at dusk, Dr. Peter Becker climbs the 99 steps up the mountain behind his home to his private
observatory and every night he studies the heavens. On one particularly clear night something strange happens.
Is Dr. Becker witnessing an invasion of space aliens? Should he rush to tell the world or wait to see if these
invaders are hostile? Write a radio script dramatizing what happens.
4. A group of eccentric physics graduate students are given the task of trying to find the way to break the most
fundamental barrier in the universe - the speed of light. If this can be accomplished space travel will be as easy as
air travel is today. Write a science fiction story explaining what happens as they collaborate to achieve their task.
5. Air pollution is choking the life out of a city neighborhood. A citizens group starts a research program to find
out what is causing the pollution and to establish a program to eliminate it, but there are very powerful people
who are opposed to their actions. As the research continues the truth is revealed. Describe the events.
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6
Name ____________________
ELEMENTS OF PHYSICS
LIGHT: OPTICS AND ELECTRICITY
Video Quiz
Directions: Answer the following true or false, or fill in the blank with the correct word to make it true.
1. We see objects either because light is reflected off their surfaces to our eyes or the
objects themselves are luminescent.
T_______ F_______.
2. The angle at which light rays bounce off a mirror is called the angle of ____________.
3. A convex mirror causes the light rays to converge.
T_______ F_______.
4. When an object is suspended in two mediums, like air and water, its image appears
broken at the boundary of the mediums. This is called ____________.
5. The sun, fire, and light bulbs are all sources of electromagnetic waves.
T_______ F_______.
6. Einstein said that objects can travel faster than the speed of sound.
T_______ F_______.
7. As long as radio waves are broadcast at different ____________ they will
not interfere with each other.
8. Television is broadcast using gamma rays.
T_______ F_______.
9. Exposure to some electromagnetic waves can lead to serious medical problems.
T_______ F_______.
10. Materials that inhibit the flow of electricity are called ____________.
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7
Name ____________________
ELEMENTS OF PHYSICS
LIGHT: OPTICS AND ELECTRICITY
Post-Test
Vocabulary
Directions: Fill in the blank with the appropriate term from the list below.
concave
conductor
convex
electromagnetic
focus
frequency
gamma
insulator
lens
light
light-year
microwave
optics
photons
radio
reflection
refraction
television
telescope
visible
1. The point at which light rays intersect when they are reflected off a concave mirror is called the ____________.
2. The ____________ spectrum consists of bands of waves that have different wavelengths and frequencies.
3. Radar uses electromagnetic waves called ___________________.
4. The distance light travels in one year is called a ____________.
True or False
Directions: Fill in the blank with True or False. If the statement is false, change it to make the statement
true. Rewrite the true statement in the space provided.
5. __________ Lenses can only converge light.
6. __________ The electromagnetic spectrum can never be used for telecommunications.
7. __________ The study of optics deals with light and vision.
8. __________ Radio and gamma waves are the same.
9. __________ Conductors stop the flow of electricity.
Essay Section
Directions: Answer the following questions in complete sentences. Use the back of this page or a separate
sheet of paper if you need more space to complete your answer.
10. Explain why objects appear to be broken at the boundary where two mediums meet.
11. Describe how modern physics explains light.
12. Why did Einstein believe that the speed of light was one of the fundamentals of the universe?
© 2003 Algonquin Educational Productions
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