Photoelectricity
Physics: AQA A Level, topic 12.2.3
Einstein's Photon Model
Albert Einstein came up with the photon model of light to overcome the ultraviolet catastrophe.
Black bodies
- A black body is an object which absorbs and emits 100% of the radiation incident upon it.
- Black bodies have a very specific emission spectrum.
The ultraviolet catastrophe
- Wave theory could not explain all of the intensity - wavelength graph for black bodies.
- This was known as the ultraviolet catastrophe.
- Wave theory predicted that the power output would continue to rise as the wavelength approached zero.
- The observation was that the power output curved back towards zero.
Einstein's photon model of light
- Max Planck suggested that electromagnetic waves might only be released in quanta.
- Einstein further suggested that electromagnetic waves can only exist in quanta, called photons.
- The photon model was able to explain the photoelectric effect, and the ultraviolet catastrophe.
Test yourself on Photoelectricity
What type of emission spectrum do black bodies have?
Which of these statements are true about the ultraviolet catastrophe?