Waves

Energy is sometimes transferred from place to

place by traveling in waves. Sound and light travel in waves. Some substances transport

energy through them in waves – like water

waves.

A wave is an energy disturbance that moves in a consistent manner. Some waves can travel through a vacuum (no matter), while

others travel through matter (called a medium). Waves that pass through a

medium do so without causing permanent

movement of the medium.

There are different types of waves with different

types of movement.

Ocean waves travel in transverse waves. A

transverse wave causes particles to move up and

down while the wave moves forward

(perpendicular to the wave motion).

Light waves also travel in transverse waves, however

light waves are electromagnetic waves.

Electromagnetic waves are able to travel either

through a vacuum or within a medium.

The Electromagnetic Spectrum

Longitudinal waves (also called compression waves)

move particles back and forth parallel to the wave

motion. Sound and earthquake waves are longitudinal waves.

Waves have properties and

scientists use these properties to

describe specific waves.

Transverse waves have crests and troughs, a crest being the highest point of displacement,

and the trough the lowest point of displacement. A node is the point where it crosses

the median line.

The wavelength of a transverse wave is defined as the distance from one

crest (or top) of a wave to the next crest on the same

side.

The wavelength of a longitudinal wave is

measured from the center of one compression to the

center of the next.

The frequency of a wave is the number of wavelengths that

pass a point in a second.

(You could count the frequency of ocean waves by standing in one

place on a dock and counting how many wave crests pass in a given

time period.)Frequency is usually measured in

Hertz or cycles per second.

The wavelength and frequency of the same wave are related. As frequency

increases wavelength decreases and as frequency

decreases wavelength increases. (Or you can say

it the other way . . . As wavelength increases,

frequency decreases, etc.).

The amplitude of a wave is measure of the amount

of displacement it causes. In other words,

the amplitude is the distance from the center

of the wave to it’s highest point.

Waves also interact with each other in various ways.

Wave interference can occur between waves.

Interference can increase wave amplitude if the

crests and troughs of the waves coincide. If the

crest and trough of two waves coincide, they can

cancel each other or reduce the amplitude.

Waves can also be reflected when they hit a

surface.

SOUND

Sound travels in longitudinal waves. Sound waves are made when an

object vibrates and causes surrounding air molecules to take on a compression wave motion. This motion

is picked up by our eardrums and translated in

our brains into sounds.

Sound waves can only travel in a medium (where

there is matter). They can not travel

in a vacuum.

Changes in wavelength of sound waves cause volume changes, while changes in frequency result in pitch

changes.

Sound waves travel at a speed of 330 m/s

in air at zero degrees Celsius.

Sound travels at different speeds in different media (water, wood, etc.) and at different temperatures.

LIGHT

Light waves are transverse.

Changes in wavelength (and thus frequency)

cause light to appear in different colors.

When white light waves (like sunlight) pass through

a prism the various wavelengths are separated

out into a spectrum.

There are light wavelengths that are

visible and some that are invisible to the human eye.

The visible spectrum includes red, orange,

yellow, green, blue, indigo, and violet light.

When red, orange, yellow, green, blue, and violet are combined, they produce

white light.

This entire visible spectrum can be seen in rainbows, puddles with oil, as light

passes through water, etc.

Light waves travel in straight lines.

When light waves pass through a small opening they cross each other

turning the image upside down.

Light waves can be reflected.

Light waves can also be refracted (bent).

When our eye looks at the pencil in water, it looks broken because the light waves have been bent by the differing substances (air is less dense than water).

Speed of LightThe velocity of light waves is consistent

at 299,792,458 m /s.

Waves are constantly surrounding us with

light, sound, and lots of other types of energy!

amplitudetrough

crest wavelength frequency

pitch electromagnetic spectrum

transverse wavelongitudinal wave

Words to Remember

Which numbered term above goes with A

on the picture?

(Answer with a number 1-5.)

1. crest2. trough3. wavelength4. node5. amplitude

Which numbered term above goes with B

on the picture?

(Answer with a number 1-5.)

1. crest2. trough3. wavelength4. node5. amplitude

Which numbered term above goes with C

on the picture?

(Answer with a number 1-5.)

1. crest2. trough3. wavelength4. node5. amplitude

Which numbered term above goes with D

on the picture?

(Answer with a number 1-5.)

1. crest2. trough3. wavelength4. node5. amplitude

Which numbered term above goes with E

on the picture?

(Answer with a number 1-5.)

1. crest2. trough3. wavelength4. node5. amplitude

What is a wave?

A: traveling energy that causes a temporary

disturbanceB: permanent movement of a

mediumC: energy that can only

travel in a vacuumD: energy that can only travel through matter

Which of the following is NOT true? Sound waves

A: are compression waves.B: are longitudinal waves.C: must travel through a

medium.D: are transverse waves.

Transverse waves

A: have a series of compressions and

rarefactions.B: move particles

perpendicular to direction of the wave.

C: have no amplitude.D: must always travel

through a medium.

Electromagnetic waves are unique because

A: they are the only type of transverse waves.

B: they are the only type of compression waves.

C: they can travel in a vacuum.

D: they require a medium in which to travel.

Which is true of light waves?

A: they are transverse waves.

B: they are electromagnetic waves.

C: they can not travel in a vacuum.

D: A & C only

In longitudinal waves

A: particles move back in forth in motion parallel to the wave motion.B: particles move up and down in motion perpendicular to the wave

motion.C: the particles in the medium are

permanently displaced when a wave passes through.

D: there is no temporary displacement of particles as the

wave moves through.

The frequency of a wave is

A: measure of the height of a wave.

B: the same as the wavelength.

C: the same as wave velocity.

D: the number of wavelengths that pass a point in a given period of

time.

As the wavelength of a wave increases

A: the frequency remains the same.

B: the velocity increases.

C: the frequency decreases.

D: the frequency increases.

Some wavelengths of light are not visible to

the human eye.

A: TrueB: False

Red light has a shorter wavelength than violet

light.

A: TrueB: False

Yellow light, X-rays, microwaves, and radio

waves are all parts of the electromagnetic

spectrum.

A: TrueB: False

Red, orange, yellow, green, blue, and violet light

wavelengths combine to form

A: black lightB: the entire electromagnetic

spectrumC: white light

D: infrared light

Sound waves are affected by temperature

and density of the medium they travel in.

A: TrueB: False

Different colors of light have different

A: crestsB: amplitudes

C: wavelengthsD: speeds

Changing the frequency of a sound wave changes the

A: volumeB: amplitude

C: pitchD: tone