P7.3+-+Reflection+and+refraction+-+plenary


 * Reflection **


 * The plane (i.e. straight) wave arriving at the barrier is "the incident wave"
 * The wave that has bounced off the barrier is "the reflected wave"


 * If the incident wave is parallel to the barrier, the reflected wave will be parallel to the barrier (but travelling in the opposite direction)
 * If the incident wave is not parallel to the barrier, then reflected wave travels away at the __same angle__ from the barrier as the angle the incident wave arrived at (only reflected through the normal to the barrier).


 * Refraction **
 * When waves travel from one medium to another, they change direction.
 * They change direction as the speed of a wave is determined by the medium, so:
 * if the medium changes the wave speed changes.
 * the __speed change in the new medium causes the direction change__.

Firm ground (= deep water in the ripple tank)

Muddy ground (= shallow water in the ripple tank)


 * Quiz ** (mini whiteboards)

1) What is the frequency of a wave? Answer 1

2) True or false?: the angle the reflected wave moves away from a barrier is the same as the angle the incident wave arrives at the barrier. Answer 2

3) True or false?: if you increase the amplitude of a wave it will move faster. Answer 3

4) True or false?: if you increase the wavelength of a wave in a uniform medium if will more faster. Answer 4

5) A wave changes direction at the boundary of a new medium because the Blank of the wave changes.