Chapter 3- Science Study Guide 3.1 Electromagnetic waves have ...

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Chapter 3
-

Science

Study Guide

3.1
Electromagnetic waves have unique traits



Electromagnetic wave
-

a disturbance that transfers energy through a field.



How do EM waves form?

o

They form when electrically charged atomic particles move, these particles exert an
electric force on each other, so they have electric fields.



What are the sources of EM waves?

o

The Sun and Technology

Electromagneti
c waves can tr
avel in a vacuum



How do EM waves travel in a vacuum?

o

Because they don’t need a medium to travel



What is the speed of EM waves called?

o

The speed of light

Electromagnetic waves can interact with a material medium



How do EM waves transfer energy?

o

By moving
potential energy from one place to another



How do EM waves convert energy from one form to another?

o

When they transfer energy to a medium


3.2 Electromagnetic waves have many uses.



What does the frequency of an EM wave determine?

o

How much
energy

the wave has.



Which has more energy, a high frequency wave or a low frequency wave?

o

High Frequency Wave

What is the electromagnetic spectrum?



How are the wavelengths in the EM spectrum related to the uses of the EM spectrum?

o

The longer the wavelengths th
e lowers the frequencies and energies, the shorter the
wavelengths the higher the frequencies and energies. Look at pages 80
-
81 for more
information.



How are EM waves measured?

o

They are measured in Hertz. One hertz equals one cycle per second.

Radio Waves



Radio waves have the

LONGEST
wavelength and the

LOWEST
frequencies

on the EM spectrum.



What does AM stand for?

o

Amplitude modulation



What does FM stand for?

o

Frequency modulation



What part of the wave is modulated (changed) to create AM?

o

The amplitude



Which part of the wave is modulated (changed) to create FM?

o

The Frequency

Microwaves



Microwaves have
shorter

wavelengths and

higher

frequencies than radio waves on the EM
spectrum.



What are two important technologies that use microwaves?

o

Microwaves and ce
ll phones



What does radar work?

o

Transmitting microwaves, receiving reflections of the waves from objects the waves
strike and converting these patterns into visual images on a screen.



How do cell phones work?



FILL IN PAGE 83

Mid
-
range wavelengths and fre
quencies on the EM spectrum


Visible Light



What is the part of the EM spectrum that humans can see called?

o

Visible light



Is this part of the EM spectrum very large or very small?

o

SMALL



What are the colors in visible light?

o

Red and violet


Infrared Light



What is infrared radiation associated with?

o

It is often associated with heat



Name 2 examples where infrared light is used.

o

Sun, fire, radiator, toaster, charcoal.


Ultraviolet Light



Because ultraviolet(UV) light has higher frequencie
s it has more
Energy



What can waves in this range do to humans? How can we prevent that?

o

It can cause damage to skin and eyes. You can use sunblock and wear sunglasses



Name beneficial uses for UV light.

o

Can be used to sterilize medical instruments and fo
od by killing harmful bacteria. It also
provide Vitamin D which is essential for good health.



How do some organisms us UV light?

o

Bees can use them to get nectar from flowers


X
-
Rays and Gamma Rays



X
-
rays and gamma rays are

short

wavelengths and
high

frequenci
es.



How are these rays produced?

o

By the sun and other stars



What are 2 uses for X
-
rays?

o

For finding bone fractures and finding dense tumors and when you get your teeth x
-
rayed.



What is a beneficial (good) use for gamma rays?

o

They can be used to
kill cancer cells and fight tumors.


3.3 The Sun is the source of most visible light.



Light



Why is light important?

o

Humans depend on it for vision, animals depend on it for food and other
necessary survival skills, and plants depend on it to make foods. With very few
exceptions, living creatures depend on light for their existence.



Where does light come from?

o

The most visible light comes from the sun, lightning, fire, and light
technologies
.



Incandescence
-

The production of light by material at high temperatures



Luminescence
-

is the production of light without the high temperature needed for
incandescence.



Bi
oluminescence
-

the production of light by living organisms.




Huma
n technologies producing light



How does an incandescent light bulb work? What is the tungsten filament? Is it efficient?

o

Light bulb works when electrical current
passes through the filament, the tungsten gets
hotter and begins to glow.

o

Tungsten filament is the part of the light bulb that heats up and produces light

o

They are not as efficient as halogen bulbs.



How does a halogen light bulb work? Is it efficient?

o

Ha
logen bulbs contain a gas, this gas combines with evaporating tungsten atoms and
deposits the tungsten back on the filament.

o

Halogen bulbs are efficient, because they last longer than incandescent bulbs.



How does a fluorescent light bulb work? Is it effi
cient?

o

They are filled with a mixture of mercury vapor and other gases that give off ultraviolet
light when an electric current passes through them.

o

Yes they are very efficient and economical



Know about sodium lights and neon lights. (notes from class)


3.4 Light waves interact with materials



Light can be reflected, absorbed or transmitted.



Transmission
-

is the passage of EM wave through a medium.



Absorption
-
is the disappearance of an EM wave into the medium.



Describe HOW materials transmit l
ight


transparent, translucent and opaque material
-
how do
light waves react to these kinds of materials? 9pg. 94)

o

Transparent
-


o

Translucent
-


o

Opaque
-



Scattering
-

the spreading out of light rays in all directions, because particle reflect and absorb
the li
ght.

o

Why is the sky blue?



Because molecules in Earth’s atmosphere scatter the blue part of visible light
more than they scatter the other wavelengths.



What happens when light is polarized?

o

All light waves vibrate in the same direction


Color and
Absorption



How is color determined?

o

Color is determined by wavelength, the different wavelengths appear as different colors
of light.



What does a prism do?

o

It is a tool that uses refraction to spread out the different wavelengths that make up
white light
. It bends some of the
wavelengths

more
than others.



Where are the primary colors helpful?

o

They are the 2 colors of light, which can be mixed to produce all possible colors.
Practical uses for primary colors are a color television or computer monitor.



Pri
mary pigments
-

are cyan, yellow, and magenta. You can mix primary pigments just as you can
mix primary color to produce all the colors.



What are primary pigments used for?

o

Primary pigment colors can be used the same as primary colors when you mix them.