- Progressive wave (moving) carry energy and does not transfer material.
- Wave caused by something making particles or fields oscillate at source.
- The oscillations pass through medium as wave travels and carries energy.
- Wave transfers energy away from source so source of wave loses energy.
- Electromagnetic waves cause things to heat up.
- X-rays and gamma knock e- out of orbits causing ionisation.
- Loud sounds cause large oscillations of air.
- Wave power can be used to generate electricity.
- Wave bounced back when hits boundary.
- Wave changes direction as enters different medium.
- Change in direction is result of wave slowing down or speeding up.
- Wave spreads out as passes through gap or round obstacle.
Displacement, x – measure in meters. (i.e. how far a point on wave has moved from its undisturbed position.)
Amplitude, A – measured in meters. (Maximum magnitude of displacement)
- Wavelength, λ - measured in meters. (Length of one whole wave oscillation or wave cycle)
- Period, T – measured in seconds. (Time taken for one whole wave cycle.)
Frequency, f – number of whole wave cycles per second passing through a given point or number of whole wave cycles given out from a source per second.
Frequency (Hz, s-1) and Period (time in s)
F = 1/T
Phase – measurement of position of certain point along wave cycle.
Phase Difference – amount by which one wave lags behind other.
- Distance travelled is WL.
- Time taken to travel 1 WL is period of wave which is equal to 1/F.
Electromagnetic Wave Speed in a Vacuum
C = 3.00 x 108 ms-1
Measuring Speed of Sound
Measuring Wave Speed in Water
- Record depth of tank with ruler.
- Use ripple tank dipper to create vibrations with regular freq. in tank.
- Dim main lights and turn on strobe light.
- Inc. freq. of strobe light from 0 until waves appear to be standing still, this is when freq. strobe light is equal to freq. of water waves.
- Use ruler and white paper below tank to measure distance between several peaks and dividing this by no. troughs in between. Distance between 2 adjacent peaks is equal to WL.
Drafted by Bonnie (Physics)