Photo Diode
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Description:
Photo diode converts light energy to electrical energy, hence they can detect presence of light. For photo diode reverse biasing is used.
Initially the rheostat is adjusted such that there is no reading shown in ammeter though there is current flowing through the circuit this current is known as dark current.
In depletion layer only atoms are present. When light is incident on atoms in depletion layer it supplies energy to electron of that atom and this electron becomes a free electron.
The free electron is pulled towards the N region and this helps in the conduction of current. This current flowing through the circuit is indicated by the ammeter and is known as photo current.
Photo current indicates the intensity/presence of light.
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