When is a light-emitting diode a receiver?

Principle

Performing this experiment is not difficult and it can be carried out in daylight as any light interference is shielded by the tube.

Benefits

• Specified for the requirements of the german final secondary-school examinations
• Especially for secondary schools
• Quantum and wave optics in a student experiment

Tasks

When is an LED a receiver? A light emitting diode or LED is an electronic semiconductor component. If a current flows through the LED in the conduction direction it emits light. Physically, semiconductors are characterised by a band gap, i.e. an energetically forbidden zone for electrons. This energy gap between the valence band and the conducting band essentially determines the electrical and optical properties. E.g. a photon whose energy is less than the band gap energy of the semiconductor cannot create an electron-hole pair. In this experiment you will determine the size of the band gaps of the LED relative to one other.