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Give the construction and working of photo emissive cell. |
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Answer» Solution :Photo emissive cell: Its working depends on the electron emission from a metal cathode due to IRRADIATION of light or other radiations. Construction: • It consists of an EVACUATED glass or quartz bulb in which two metallic electrodes - that is, a cathode and an anode are fixed. • The cathode Cis 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 . • A potential difference is APPLIED between the anode and the cathode through a galvanometer G. Working: . When cathode is illuminated, electrons are emitted from it. These electrons are attracted by anode and hence a current is PRODUCED which is measured by the galvanometer • For a given cathode, the magnitude of the current depends on (i) the intensity to incident radiation and (ii) the potential difference between anode and cathode 
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