Waves

Transverse wave

• the vibrations are at right angles to the direction of energy transfer/direction of travel.

• Particles move up and down on the spot. They don’t move across.

Longitudal wave

• the vibrations are parallel to the direction of travel (the direction the wave is travelling in.)

Amplitude

• the height of the wave (from the rest position to the top of the peak.)

Frequency

• Frequency is the number of cycles per second. (up + down = 1 wave)

• Frequency is measured in Hertz (Hz)

Wavelength

• the distance between 2 peaks of 2 troughs (2 equivalent points.)

Period

• How long one cycle takes.

• Measured in seconds

• symbol T

Equation for frequency

Frequency = 1/period

Equation for wave speed

wave speed = frequency x wavelength

Waves transfer energy without…

transferring matter

all waves can reflected…

• Reflected - can be reflected at the boundary between two different materials.

• angle of incidence = angle of reflection

all waves can be refracted…

• Refracted - The density of a material affects the speed that a wave will be transmitted through it.

• The denser the transparent material, the more slowly light travels through it.

• Glass is denser than air, so a light ray passing from air into glass slows down.

explain the change in the frequency and wavelength of a sound wave when its source is moving - The Doppler Effect

• when a stationary object emits waves, the waves spread out symmetrically.

• standing in front of an object moving towards them:
  - wavelength gets shorter (waves get squashed) and the frequency gets higher = higher pitch

• standing behind an object moving away from them: 

  - The wavelength appears to get longer (waves get stretched) and the frequency gets lower = lower pitch

The Doppler Effect

The apparent change in observed wavelength and frequency of a wave emitted by a moving source relative to an observer.