Coolest Wave Ever Seen!!!

Waves • Waves transport energy without the large-

scale transport of matter.

“At a recent staff meeting, it was announced that Mrs. Hatfield

had been named Female Chemistry Teacher of the Month. The

excitement passed through the entire Science Department!!!”

Waves(cont.) • The medium through which the wave travels may

experience some local oscillations(or vibrations) as the wave passes, but the particles in the medium do not travel with the wave.

What is “the medium”?

• But what is meant by the word medium? A medium is a substance or material which carries the wave. You have perhaps heard of the phrase news media. The news media refers to the various institutions (newspaper offices, television stations, radio stations, etc.) within our society which carry the news from one location to another. The news moves through the media.

2 types of waves: 1. Mechanical Waves—waves that require a

material medium to travel through. • Can’t travel through empty space.

2. Electromagnetic Waves—waves that do not require material medium.

• Can travel through empty space.

2 ways that waves travel:

Transverse Waves • Displacement of the

medium is perpendicular to the propagation of the wave.

Longitudinal Waves – Or compressional waves

• Displacement of the medium is parallel to the propagation of the wave.

Characteristics of Waves

Characteristics of Waves(cont.)

• Crests—highest parts of waves.

• Troughs—lowest parts of waves.

Characteristics of Waves(cont.)

•Wavelength( l)—the distance advanced by a wave in one period. – Typically from crest to crest(or trough to trough), but can be from any

point on a wave to the corresponding point on the next wave.

Characteristics of Waves(cont.) • Amplitude(A)—maximum displacement of the

wave from the equilibrium position. – Measured in meters(m)

– Amplitude is a measure of the amount of energy carried by a wave.

Amplitude(A)

Amplitude and Wavelength of Longitudinal Waves

Amplitude and Wavelength of Longitudinal Waves

Wavelength is measured compression to compression(or

rarefaction to rarefaction)!

Amplitude is measured by the density of the compressions!

Characteristics of Waves(cont.)

• Frequency(f)—the number of waves that pass a given point in an amount of time.

• Unit is the Hertz(Hz)

Frequency(cont.)

Frequency is related

to the pitch of a

sound wave.

Characteristics of Waves(cont.)

• Wave velocity—the speed of the wave.

If the crest of an ocean

wave moves a

distance of 20 meters

in 10 seconds, then the

speed of the ocean

wave is 2 m/s.

Which letter represents the crest?

Which letter represents the trough?

Which letter represents the wavelength?

Which letter represents the amplitude?

What is the value of the amplitude in the wave below?

A. 2 m

B. 1 m

C. 4 m

D. 8 m

The wave below takes 2 seconds to pass. What is the frequency of the wave?

A. 4 Hz

B. 3 Hz

C. 2 Hz

D. 1 Hz

Wave velocity

is the velocity in m/s

is the frequency in Hertz(Hz)

is the wavelength in meters

A particular wave has a frequency of

250 Hz and a wavelength of 1.2 m.

How fast does the wave move?

v = f x l

= (250 Hz)(1.2 m) = 300 m/s

v = ?

f = 250 Hz

l = 1.2 m

A sound wave has a velocity of 331 m/s

and a frequency of 400 Hz. What is the

wavelength of the sound wave?

v = 331 m/s

f = 400 Hz

l = ?

v = f x l l = v/f l = 331/400

l = .83 m

A particular wave has a frequency of 24 Hz and a velocity of 3 m/s. Determine the wavelength.

A. 72 m

B. 8 m

C. 4 m

D. .125 m

A wave at the ocean has a frequency of 8 Hz and a wavelength of 2 m. Determine the velocity of the wave.

A. .25 m/s

B. 4 m/s

C. 16 m/s

D. 32 m/s