2.3. Wave Phenomena (C3 - AHL)

When a wave hits the boundary between two different media, several things can happen:

• Reflection: Part of the wave bounces back into the original medium.

• Transmission (Refraction): Part of the wave enters the new medium and changes speed, which leads to bending of the wave (refraction). ​​

• Change in wavelength:
  Frequency stays the same, but wavelength changes due to change in speed.

• Partial absorption: Some energy may be lost (e.g. to heat).

These behaviors are explained using boundary conditions and principles like wavefront continuity and conservation of energy.

When waves pass through an aperture or around obstacles, they undergo diffraction — they spread out.

The degree of diffraction depends on the relationship between:

• The wavelength λ

• The aperture width a

Greatest diffraction occurs when: λ≈a

Represented using wavefront diagrams (Huygens’ Principle):

• Wavefronts curve outward after passing through a narrow gap.

• Narrower aperture → more spreading.

This is superposition — the total displacement is the sum of the individual displacements

If the waves are in phase, we get constructive interference: amplitudes add → louder sound, brighter light, etc.

If the waves are out of phase (180°), we get destructive interference: amplitudes cancel → silence or darkness.

This principle explains phenomena like:

• Interference patterns (e.g. double-slit experiment)

• Standing waves on strings or in pipes