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Question
Give the construction and working of photo emissive cell.
Solution
Photo emissive cell: Its working depends on the electron emission from a metal cathode due to irradiation of light or other radiations.
Construction:
1. It consists of an evacuated glass or quartz bulb in which two metallic electrodes – that is, a cathode and an anode are fixed.
2. The cathode C is semi-cylindrical in shape and is coated with a photo sensitive material. The anode A is a thin rod or wire kept along the axis of the semi-cylindrical cathode.
3. A potential difference is applied between the anode and the cathode through a galvanometer G.
Construction of photo cell
Working:
When the cathode is irradiated with suitable radiation, electrons are emitted from it. These electrons are attracted by the anode and hence a current is produced which is measured by the galvanometer.
For a given cathode, the magnitude of the current depends on
- the intensity to incident radiation and
- the potential difference between anode and cathode.
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