Light and colour

• What is total internal reflection?

  When light is completely reflected back at a boundary between two mediums
• Under what condition does total internal reflection occur?

  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 which 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 colour of visible light has the highest frequency?

  Blue
• What colour of visible light has the largest wavelength?

  Red
• What is meant by the term ‘specular reflection’?

  Rays are reflected from a smooth surface in a single direction
• What is meant by the term ‘diffuse reflection’?

  Reflection from a rough surface which causes scattering
• How does a red colour filter work?

  A red filter absorbs all wavelengths of light other than those in the red range of the spectrum
• What does the term “opaque” mean?

  Not see-through
• What governs the colour of an opaque object?

  Different objects reflect different wavelengths of light by different amounts
• What happens to the wavelengths of light that aren’t reflected by an opaque object?

  Any wavelengths that aren’t reflected are absorbed by the object
• What colour does an object appear if all wavelengths are absorbed?

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

  White