8 INVESTIGATING
LIGHT AND SOUND
EQ: How are light waves and sound waves
similar and how are they different?
Place an X next to each item that reflects light
■ Water
wax paper
the moon
brand new penny
■ Gray rock
tomato soup
rusty nail
old tarnished penny
■ Leaf
crumpled paper
clouds
■ Mirror
shiny metal
soil
■ Glass
■ Sand
■ Potato skin
smooth sheet of aluminum foil
Explain
■ 1. Mirror and Laser- When the laser light bounced off the mirror it was
reflected at an angle onto the board.
■ 2. The laser light was absorbed and transformed into thermal energy
when it hit the wood block
■ 3. Light transmission occurred when the laser light went straight
through the clear glass and appeared on the front screen or board
■ 4. When the light refracted as it traveled through the air and then to
the water you could tell it had changed speed because the pencil
appeared bent.
Light energy is a form of energy that is carried by
___________________ waves. These are waves that can travel
through empty space and matter. Electromagnetic waves
travel in straight lines called rays and spread out in all
directions from the source.
Light energy is a form of energy that is carried by
electromagnetic waves. These are waves that can travel
through empty space and matter. Electromagnetic waves
travel in straight lines called rays and spread out in all
directions from the source.
They travel very quickly in 2.___ and slow down when they travel
through matter. Electromagnetic waves are classified by their
3._______, which is the distance from any point on one wave to
a corresponding point on an adjacent wave.
They travel very quickly in space and slow down when they travel
through matter. Electromagnetic waves are classified by their
wavelength which is the distance from any point on one wave to
a corresponding point on an adjacent wave.
The types of electromagnetic waves, in order of decreasing
wavelength, are radio waves, microwaves, infrared waves,
visible light, ultraviolet light, x-rays and gamma rays.
Electromagnetic waves have many common uses such as cell
phones which use microwaves, remote controls that use
infrared rays, and gamma ray that can be used for radiation
treatment of cancerous cells. Visible light is the only form of
electromagnetic waves that can be seen by humans.
Visible light, also known as white light, is a combination
of red, orange, yellow, green, blue, indigo and violet
light. Three things can happen to light when it hits the
surface of matter. The light can be reflected by the
matter, it can pass through the matter, or it can be
absorbed by the matter. This is determined by the
surface it strikes.
When light strikes a transparent object, such as glass, most of
the light will pass through. If light passes through 2 different
transparent objects, such as water and air, the light will change
speed causing the light to bend or refract. Translucent objects,
such as plastic Tupperware, allow some of the light to pass
through while the rest is either absorbed or reflected. Objects
that absorb or reflect all light are known as opaque and include
things such as wood. When we see color, we are seeing the
reflection of light. A red object will reflect red light and absorb
every other color of visible light.
Electromagnetic energy is not the only form of energy that
travels in a wave. Sound travels in a wave known as a
mechanical wave and unlike an electromagnetic wave; it must
have a medium to travel through. Sound waves cannot travel
through empty space. Sound is produced when an object
vibrates. The vibrating object pushes the particles of matter
next to it and causes them to compress (squeeze together).
That compressed matter, in turn, compresses the matter next to
it.
Sound waves travel in all directions away from their sources. Like
light, sound travels at different speeds through different
materials. In general, sound travels faster through solids than
through liquids, and faster through liquids than through gases.
Sound waves also travel faster through a warmer medium than
through a cooler medium. The wavelength, or frequency, of a
sound wave determines the pitch of the sound that is heard. A
shorter wavelength results in a higher pitch, such as a flute, and
a longer wavelength results in a lower pitch such as a bass
guitar.
Light waves
Both
Sound Waves
• Can travel through
space
• classified by
wavelength
• Travels slower in
objects with greater
density
• Does not require a
medium
• Transfers energy in
all directions from
the source
• Changes speed
• Travels through
solids, liquids &
gases
• Higher
frequency=higher
energy
• Can be reflected,
refracted, absorbed
• Higher
frequency=higher
pitch
• Compresses matter
• Travels faster in
objects with greater
density
• Requires a medium