Wave Phenomena

There are three wave phenomena that can occur when a wave meets a boundary:

• Reflection
• Refraction
• Diffraction

Reflection

When light 'hits' a mirror, the light . We say it as been . We define the angle at which a ray hits a mirror as the angle of '. This is measured, not from the mirror surface but from a line at 90° to it. We call this imaginary line the . The reflect ray leaves the mirror at the angle of which is also measures from the normal.

The angle of reflection equals the angle of incidence.

Refraction

Refraction is the change in of a wave, at an interface between two media that creates a change in .

Water waves travel slower in shallow water than in deep. This is why waves break. The bottom of the waves slows down as the water becomes shallower up the beach. The top of the wave continues at its original speed and so 'falls' forward.

If we consider light then the media could be air and glass. The light travels slower in the glass than in air. When a ray of light enters a glass block at an angle to the interface (edge) it is bent away from the normal. When rays leave a glass block they bend towards the normal. We have seen that the bigger the angle of incidence then the the ray is refracted (bent).

Diffraction

When a wave moves through a , or past an obstacle, it from the edges. This is diffraction.

Significant diffraction only occurs when the of the wave is roughly the same size as the gap.