Wave behaviour at boundaries

When a wave encounters a boundary between two different materials (a material interface), several things can happen depending on the properties of the materials and the wavelength of the wave.

1. Absorption:

Waves are absorbed by the second material. When this happens, the wave transfers its energy to the material. Often, this energy is transferred to the material's thermal energy store, leading to heating.

2. Reflection:

Waves are reflected off the boundary between the two materials. The wave is neither absorbed nor transmitted, but instead bounces back from the second material. This is how echoes are created when sound waves reflect off hard surfaces like walls or cliffs.

In reflection:

• The angle of incidence (incoming angle) is equal to the angle of reflection (outgoing angle).

3. Transmission and Refraction:

Waves are transmitted through the second material. When waves pass into the second material, they may change direction. This change in direction is called refraction.

Refraction occurs because the wave changes speed as it enters a new material, which can make it bend.

Refraction is used in:

• Lenses (e.g., glasses, camera lenses) to focus light.
• Communication systems, like fibre optics, to transmit data.

What Determines Wave Behaviour?

The way a wave behaves at a boundary depends on:

1. The wavelength of the wave (e.g., shorter wavelengths are more likely to be reflected).
2. The properties of the material (e.g., denser materials may absorb or refract more energy).