Explain the photoelectric effect, when does it occur and what is its significance in understanding the nature of light ? (6)

metal (unlike insulators ) contains free electrons (1)

kinetic energy transferred from the light incident on the surface to the free electrons (1)

The maximum kinetic energy of the electrons depends on the frequency (or wavelength) of light and not on the intensity (1)

SOME of the free electrons will be liberated from the surface (1)

No electrons are liberated from the surface until a certain energy /frequency / wavelength of light is incident ie. the threshold energy /frequency / wavelength . (1)

Proves that light travels in discrete quanta (1)