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CHAPTER 22
SECTION 1
1. Light, just like sound, travels in waves.
Sound travels as a longitudinal wave, light
travels as a transverse wave.
Light: An Electromagnetic Wave
1. Light is a type of energy. It is also known
as electromagnetic energy.
2. An electromagnetic wave is a wave that can
travel through empty space or through
matter.
3. An electromagnetic wave has a magnetic
field and an electric field that travel at right
angles to one another.
4. In an electromagnetic wave the electric and
magnetic field are also at right angle, or
perpendicular to the direction the wave is
moving.
5. The electromagnetic wave is produced by
the vibration of a photon. A photon is an
electrically charged particle.
6. Every electrically charged particle has an
electric field around it. When the particle
vibrates, it causes the electric field to
vibrate.
7. If you have a moving electric field, you
also create a magnetic field.
8. The vibration of the electric and magnetic
field produces the electromagnetic wave.
9. The transfer of energy by electromagnetic
waves is radiation.
The Speed of Light
1. Nothing travels faster than the speed of
light.
2. In a medium-free environment, light travels
at 300,000 km/sec (or 9.5 trillion km/year).
3. In an environment with a medium, the light
is slowed by the medium.
4. The light waves from the sun are the major
energy sources on Earth.
SECTION 2
1. Electromagnetic waves can be arranged in
order according to wavelength and energy
level.
Characteristics of Electromagnetic Waves
1. All electromagnetic waves travel at the
same speed in a vacuum.
2. The medium that any electromagnetic wave
travels through will affect the wave’s
speed.
3. The electromagnetic waves can be arranged
by wavelength and energy on the
electromagnetic spectrum. The spectrum is
divided into regions based on wavelength.
4. The spectrum in order from longest
wavelength, lowest energy to shortest
wavelength, highest energy:
radio wave
microwave
infrared
visible light
ultraviolet
x ray
gamma ray
5. Infrared waves are responsible for the
warmth you feel on a sunny day. The
energy of the wave causes the particles in
your skin to vibrate more, increasing the
temperature and causing you to feel
warmer.
6. Visible light is a band of colors: ROY G
BIV
7. The different colors of light have different
wavelengths and energy levels.
SECTION 3
1. Electromagnetic waves interact in various
ways that affect the way we view our
universe.
Reflection
1. The law of reflection says that the angle at
which light strikes a barrier will be equal to
the angle at which it reflects off the barrier.
2. If an object produces its own light, it is
luminous. If it reflects the light of another
object it is said to be illuminated.
Absorption and Scattering
1. As light travels away from the object that
produced it, the light gets dimmer and
dimmer. This is due to absorption and
scattering.
2. When energy is transferred from a light
wave to particles of matter that is
absorption. This causes the light to
become dimmer.
3. Scattering is an interaction between light
and matter that causes the light to change
direction.
4. After colliding with matter, light scatters in
all directions. Light with a shorter
wavelength is scattered more than that with
a longer wavelength. This is why the sky
appears blue.
Refraction
1. Refraction is the bending of light as it
passes from one medium to another.
2. Refraction occurs because the speed of
light varies according to the medium it is
traveling through.
3. The part of the wave that first enters the
new medium starts traveling at a different
speed before the rest of the wave does.
This causes the bending to occur.
4. Refraction results in optical illusions.
5. Refraction also results in the formation of
rainbows as the sunlight is refracted by the
water drops in the atmosphere.
6. Each color of light has a different
wavelength. The colors with the shortest
wavelength bend more than the ones with
longer wavelength.
Diffraction
1. Diffraction is the bending of waves around
barriers or through openings.
2. The amount a wave diffracts is determined
by its wavelength and the size of the
barrier/opening.
3. Light waves cannot diffract very well
around large objects.
Interference
1. Interference occurs when 2 or more waves
overlap.
2. Interference may be destructive, which
results in less amplitude than the original
wave, or it may be constructive, which
results in greater amplitude than the
original wave.
SECTION 4
1. Whenever light strikes matter it interacts
with the matter.
Light and Matter
1. Reflection happens whenever light bounces
off of an object. It is reflected light which
allows us to see objects that do not produce
their own light.
2. Absorption occurs whenever light energy is
transferred to matter. Absorption causes
the matter molecules to become more
energized.
3. Transmission is the passing of light waves
through matter.
a. Matter through which light is easily
transmitted is said to be transparent.
EXAMPLE: glass
b. Translucent matter transmits light but
scatters it as it passes through.
EXAMPLE: wax paper
c. Opaque matter does not transmit any
light. EXAMPLE: metals
Colors of Objects
1. The color that an object appears to be is
determined by the wavelength of light
that reaches your eyes.
2. The color of light that is reflected by an
object is the color that reaches your eyes.
3. If an object appears white it is reflecting
all colors and absorbing none.
4. If an object appears black, it is absorbing
all colors and reflecting none.