EXAM GUIDELINES P1
Optical Phenomena and Properties of Materials
(This section must be read in conjunction with the CAPS, p. 132–133.)
Photo-electric effect
- Describe the photoelectric effect as the process whereby electrons are ejected from a
metal surface when light of suitable frequency is incident on that surface.
- State the significance of the photoelectric effect.
- Define threshold frequency, fo , as the minimum frequency of light needed to emit
electrons from a certain metal surface.
- Define work function, Wo , as the minimum energy that an electron in the metal needs to
be emitted from the metal surface.
- Perform calculations using the photoelectric equation:
- Explain the effect of intensity and frequency on the photoelectric effect.
Emission and absorption spectra
- Explain the formation of atomic spectra by referring to energy transition.
- Explain the difference between atomic absorption spectra and
atomic emission spectra.
- An atomic absorption spectrum is formed when certain frequencies of electromagnetic
radiation that passes through a medium, e.g. a cold gas, is absorbed.
- An atomic emission spectrum is formed when certain frequencies of electromagnetic
radiation are emitted due to an atom's electrons making a transition from a high-energy
state to a lower energy state.