Light and Colour

• Total internal reflection.

  When light is completely reflected back at a boundary between two mediums, it occurs when light meets a less dense medium at an angle of incidence larger than the critical angle.
• What is the critical angle?

  The angle of incidence that causes the angle of reflection to be 90 degrees.
• What determines the colour of visible light waves?

  The wavelength and frequency of the light waves.
• What is ‘specular reflection’?

  Rays reflected from a smooth surface in a single direction.
• What is ‘diffuse reflection‘?

  Reflection from a rough surface which causes scattering.
• What governs the colour of an opaque object?

  Different objects reflect different wavelengths of light by different amounts, the wavelength that are most strongly reflected determine the colour.
• What happens to the wavelengths of light that aren’t reflected by an opaque object?

  Absorbed by the object.
• What colour does an object appear if all the wavelengths are reflected by equal amounts?

  White.