SP4- Waves Flashcards
Transverse waves
- particles move up and down at right angles to direction the wave is moving.
- particles not carried along with the wave.
- (e.g sea waves, light waves)
Longitudinal waves
- particles move back and forth in same direction as wave is traveling.
- (e.g sound waves)
Electromagnetic waves
- transverse wave.
- do not need a medium (material) through which to travel.
Frequency
- number of waves passing a point each second.
- measured in Hertz (Hz).
- 1 Hz = 1 wave passing per second.
Period
- length of time it takes one wave to pass a given point.
Wavelength
- distance from a point on one wave to point in the same position on next wave.
- measured in Metres (M).
Amplitude
- maximum distance of the point on the wave away from its rest position.
- measured in Metres (M).
- greater amplitude of sound wave = louder the sound.
Velocity
- speed of wave in the direction its travelling.
Wave speeds
- speed (m/s) = distance (m) / time (s)
- wavespeed (m/s) = frequency (Hz) X wavelength (m)
Refraction
- refraction happens at INTERFACE (boundary) between the two media.
- line at right angles to the interface = NORMAL LINE
- light travelling along normal line DOES NOT refract.
- light refracts TOWARDS the normal when SLOWS down
- light refracts AWAY from the normal when SPEEDS up
How does change in speed of a wave affect its direction?
- bend of refraction depends on
. how fast light travels into the two media
. angle of light hitting the interface. - greater the difference inspeed
Transmitted
- wave passes through the material and is not absorbed or transmitted.
Absorbed
- Wave disappears as the energy it is carrying is transferred to the material.
Why can a prism be used to split up visible light into the colours of the rainbow?
- colours in light change speed by different amounts when transferred from air to glass = refracted through varying angles.
Sound wave passes a gas or liquid
- particles vibrate backwards and forwards
Sound waves passes a solid
- some of energy it’s transferring is reflected
- some energy is transmitted through solid or absorbed
- sound wave causes change in pressure on surface = causes particles to vibrate = disturbance is passed from air to solid
Human Ear - internal structure as sound wave passes through
1) sound wave enters ear canal
2) sound wave vibrates ear drum
3) vibrations passed on to tiny bones which amplify
4) vibrations passed on to liquid inside cochlea
5) hairs inside cochlea detect vibrations - create impulses
6) impulses travel along neurones in the auditory nerve to reach brain
How does the cochlea work?
- coiled tube containing liquid
- detects different frequencies (20hz - 20000hz)
- membrane in middle of tube is thicker and stiffer at base and thinner at apex
- part that vibrates depends on frequency
- hairs detect vibrations
