Question

Describe construction and working of a photo cell with the help of neat diagram.

Answer 1

Construction:

• It consist of an evacuated glass bulb or tube containing two electrodes anode and cathode.
• The cathode is semi-cylindrical photosensitive metal plate (E) and the anode is in the form of metal rod.
• The glass bulb is fitted on nonconducting base provided with two pins for external connection as shown in figure given below.

Working:

• The experimental circuit is as shown in the figure.
• The cathode is connected to negative terminal and anode is connected to positive terminal of battery (HT) with microammeter.
• When light of suitable wavelength falls on the cathode, photoelectrons are emitted.
• These electrons are attracted towards the anode due to applied electric field.
• The generated photocurrent is noted from the microammeter.
• This current is directly proportional to the intensity of incident light.