Reflection and Refraction

Reflection of Waves (p 267) When a wave reaches a boundary between 2 media, some or all of the wave reflects. Particles also reflect. The law of reflection states the angle of reflection equals the angle of incidence:

(p 267) The normal is perpendicular to the reflecting surface Incidence means incoming The angle of incidence and reflection are measured from the normal

Refraction of Waves (p 267) Refraction occurs when a wave changes the direction in which it is moving This is caused by a change in speed as the wave passes from one medium to another

(p 268) The Law of Refraction (Snell’s Law) states:

The constant “n” is called the index of refraction and measures the amount of bending (add to bottom p 268) Remember: Frequency only changes if you change the actual wave ( the wave source)

Reflection of a Wave at a Boundary When a wave or wave pulse hits a boundary (between two substances or media) another, some of the energy carried in the original wave is transmitted into the new medium & some energy is reflected. The pulse that passes into the new medium (i.e. TRANSMITTED) is always ERECT. The pulse that bounces off the new medium (i.e. REFLECTED) depends on the media.

Two Densities & Unfixed end the transmitted pulse is always erect the REFLECTED pulse that occurs when moving FROM a LESS dense medium TO a MORE dense medium always INVERTED (upside down). the REFLECTED pulse that occurs when moving FROM a MORE dense medium TO a LESS dense medium, is always ERECT (in the same direction as the original pulse).

The animation on the next slide depicts the boundary behavior of a pulse which is moving along a less dense medium and incident towards (i.e. approaching) a more dense medium. Note that when the pulse reaches the end of the medium, a portion of its energy is transmitted into the more dense medium (in the form of a transmitted pulse), a portion of its energy remains in the less dense medium (in the form of a reflected pulse).

One Density and a Fixed End the REFLECTED pulse that is produced from striking a fixed boundary is both INVERTED & REVERSED:

Reflection at a Fixed End

One density, end unfixed The REFLECTED pulse produced from reaching and returning from an UNFIXED end is REVERSED and erect.

Reflection at an Unfixed End