Physics Unit 5Waves – Light & Sound

Wave• A rhythmic disturbance that transfers

energy through matter and/or a vacuum

• Material a wave travels through is called the medium

• 2 types of waves:

1. Transverse

2. Compressional (Longitudinal)

Transverse• Matter in the wave moves at right angles to

the direction of the wave front

mid line (resting position)

Crest

Trough

amplitude

Wavelength (λ)

Examples: gamma radiation, x-ray, UV, visible light, infrared, microwave, radio, TV, water

Compressional (Longitudinal)

• Matter moves in the same direction as (along with) the wave front

compression

rarefaction

λ

Example: sound

Transverse & Compressional

• Amplitude (A)

-determined by amount of energy

• Wavelength (λ)

-determined by the wave frequency

• Frequency (f)

-number of waves per second

-measured in hertz (Hz)

Transverse & Compressional• Velocity (v)

v = λf

-varies based on temperature, what it is traveling thru

-stays the same in a given medium

• velocity of light (all transverse waves)

- 300,000,000 m/s

• velocity of sound (longitudinal waves)

-330 m/s

Frequency Comparisons

• Transverse • Longitudinal

High frequency

-purple light

Low frequency

-red light

High frequency-High pitch

low frequency-low pitch

Amplitude Comparisons• Transverse • Longitudinal

High amplitude

-bright light

Low amplitude

-dim light

High amplitude-loud

low amplitude-quiet

Transverse vs. Longitudinal

Check up

Which has a longer λ?

-A

Which has higher frequency?

-B

Which has higher amplitude?

-both same