Warm Up

• What is a wave?

• Name all the parts of a wave you can think of

• Name all the different kinds of waves you can think of

Wave – a disturbance that travels through space and time, usually transmitting energy.

Properties of Waves

Waves have several parts to them…

The normal is where the medium would be if there were no wave.

The normal is shown as a dotted line here.

The crest is the part of the wave that goes above the normal.

The trough is the part of the wave that goes below the normal.

Crest, Trough, Wavelength, Amplitude.

Momentum

Crest, Trough, Wavelength, Amplitude.

Momentum

Crest

Crest, Trough, Wavelength, Amplitude.

Momentum

Crest

Trough

Crest, Trough, Wavelength, Amplitude.

Momentum

Wavelength

Crest, Trough, Wavelength, Amplitude.

Momentum

Wavelength

Am

plit

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e

Properties of Waves

Properties of Waves

Mechanical Wave – a wave that requires a material in which to travel.

Properties of Waves

Electromagnetic (visible light) waves, radio waves, microwaves and X-rays can travel through a vacuum like space

Properties of Waves

Properties of Waves

2 Types of waves:Properties of Waves

2 Types of waves:Transverse Waves – a wave whose particles vibrate perpendicularly to the direction of wave motion.

Properties of Waves

Crest

Properties of Waves

2 Types of waves:Transverse Waves

Trough

So remember… when the particles move

perpendicular to the energy, you have a transverse wave.

2 Types of waves:Longitudinal (Compression) Wave – a wave whose particles vibrate parallel to the direction of wave motion.

Properties of Waves

2 Types of waves:Longitudinal Wave

Properties of Waves

2 Types of waves:Longitudinal Wave

Properties of Waves

Compression

Rarefaction

Longitudinal waves don’t have crests and troughs like transverse waves.

Instead they have areas of bunched up particles,

and areas of spread apart particles.

The areas of bunched up particles are

compressions. (look up top!)

The areas of spread apart particles are

rarefactions. (look on the

bottom)

On a transverse wave, the wavelength is the distance between two crests or troughs.

On a longitudinal wave, wavelength is the distance between compressions or

rarefactions.

Instead of writing “wavelength” all the time, scientists use the Greek letter lambda to represent wavelength.

Lambda =

wavelength

Properties of Waves

Wavelength

The amplitude of a transverse wave is how far from the normal the medium moves.

The amplitude of a longitudinal wave is the

thickness of the compressions.

The amplitude of a wave tells us how much energy is in the wave. Larger amplitude means

more energy!

AmplitudeProperties of Waves

Frequency (f) – Hertz – number of complete cycles (1 crest and 1 trough) per second.

(2 Hz = twice per second)

Properties of Waves

The light blue wave here has the smallest frequencyfrequency. You can tell because it has the longest wavelengthwavelength.

The blue wave has the greatest frequencyfrequency. You can see it has the smallest wavelength.

FrequencyFrequency is measured in a unit called hertz (Hz).hertz (Hz).

One Hz Hz means that one crest passes a given point each second.

Period (T) – amount of time required for one complete vibration.

Properties of Waves

Properties of Waves

Properties of Waves1 second

Frequency and Period are inversely related.

High frequency = low periodLow frequency = high period

Properties of Waves

Frequency and Period are inversely related.

f = 1 T = 1 T f

Properties of Waves

Wave Speedv = f λ

v = velocity of wave (m/s)f = frequency (Hz)λ = wavelength (m)

Properties of Waves

The piano string tuned to middle C vibrates at 264 Hz. Assuming the speed of sound is 343m/s, what is the wavelength of the sound?

Properties of Waves

The piano string tuned to middle C vibrates at 264 Hz. Assuming the speed of sound is 343m/s, what is the wavelength of the sound?

Properties of Waves

v = f λ

The piano string tuned to middle C vibrates at 264 Hz. Assuming the speed of sound is 343m/s, what is the wavelength of the sound?

343 =

Properties of Waves

v = f λ

The piano string tuned to middle C vibrates at 264 Hz. Assuming the speed of sound is 343m/s, what is the wavelength of the sound?

343 = 264(λ)

Properties of Waves

v = f λ

The piano string tuned to middle C vibrates at 264 Hz. Assuming the speed of sound is 343m/s, what is the wavelength of the sound?

λ = 1.3m

Properties of Waves

v = f λ

Green Light has a wavelength of 5.25x10-7

m. If the frequency is 5.71x1014 Hz, how fast

does green light travel?

Cool Down

Green Light has a wavelength of 5.25x10-7m. If the frequency is 5.71x1014 Hz, how fast does

green light travel?

Momentumv = f λ

Green Light has a wavelength of 5.25x10-7m. If the frequency is 5.71x1014 Hz, how fast does

green light travel?

v = (5.71x1014)(5.25x10-7)

Momentumv = f λ

Green Light has a wavelength of 5.25x10-7m. If the frequency is 5.71x1014 Hz, how fast does

green light travel?

v = 299,775,000m/s2.99x108m/s

Momentumv = f λ

Exit Slip

1. Draw a diagram of a wave and label the parts