called photosensitive materials . . . Effect of intensity of incident light on photoelectric current Experimental setup The apparatus shown in Figure .
is employed to study the phenomenon of photoelectric effect in detail. S is a source of electromagnetic waves of known and variable frequency ν and intensity I . C is the cathode (negative electrode) made up of photosensitive material and is used to emit electrons. The anode (positive electrode) A collects the electrons emitted from C .
These electrodes are kept in an evacuated glass envelope with a quartz window that permits the passage of ultraviolet and visible light. The necessary potential difference between C and A is provided by high tension battery B which is connected across a potential divider arrangement PQ through a key K . C is connected to the centre terminal while A to the sliding contact J of the potential divider. The plate A can be maintained at a desired positive or negative potential with respect to C .
To measure both positive and negative potential of A with respect to C , the voltmeter is designed to have its zero marking at the centre and is connected between A and C . The current is measured by a micro ammeter m A connected in series. If there is no light falling on the cathode C , no photoelectrons are emitted and the microammeter reads zero. When ultraviolet or visible light is allowed to fall on C , the photoelectrons are liberated and are attracted towards anode.
As a result, the Photo sensitive plate Quartz window Evacuated glass tube V µA