Refraction
Refraction is the change of direction of a wave when it goes form medium to medium.
Waves bend:
Waves bend:
- Away from the perpendicular if medium 2 is less dense than medium 1
- Toward the perpendicular if medium 2 is more dense than medium 1
In this example, the wave refracts away from the perpendicular. (Air is less dense than water.)
Optical reversibility:
- Any actual ray of light in an optical system, if reversed in direction, will retrace the same path backward