Waves & Sound

Wave

A means of transferring energy from one place to another

transversal wave

Direction of the vibration is perpendicular to the direction of the wave

Longitudinal wave

Direction of the vibration is in the same direction to which the wave is travelling

Wavelength

The distance from one point on the wave to the corresponding point on the next cycle

Frequency

A measure of the number of oscillations (full cycles) of the wave per second. ( Number of crests that pass a point in one second )

Periodic time

The time taken for one complete cycle

Frequency, velocity & wavelength

C = f(wavelength)

Periodic time & frequency

T = 1/f

Diffraction

The spreading of waves around a split/gap or an obstacle. This effect is only significantly noticeable if the split width is approximately the same size as the wavelength of the waves.

Coherent sources

If two waves have the same frequency and are in phase. “ in phase ” means crests stay over crests and troughs stay over troughs.

Interference

This occurs when waves from two sources meet to produce a wave of different amplitude.

The Doppler effect

The apparent change in the frequency of a wave due to the relative motion between the source of the wave and the observer

Stationary wave

When 2 waves of the same frequency and amplitude moving in opposite directions meet, they interfere with eachother

A medium

Sound needs this in which to travel

Natural frequency

The frequency an object vibrates at when ‘disturbed’ & free to vibrate

Resonance

The transfer of energy between bodies of the same frequency. Eg. Singer & wine glass

Polarisation

A wave that vibrates in one plane only. Eg. Sunglasses

Harmonics

Multiples of fundamental frequencies

Calculating the speed of air. ( 1/f & l )

C = 4f( l + 0.3d )

Y = mx + c

m = f/1 m = c/4

Measuring ‘T’. ( f & root’T’ )

F=(1/2l)(rootT/meu)