Describe an experimental arrangement to study photoelectric effect.

Explanation

Experimental setup :
The apparatus is employed to stud the phenomenon of photoelectric effect in detail.
S is a source of electromagnetic waves of known and variable frequency v 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 taken in an evacuated glass envelope with a quartz window that permits the passage of ultraviolet and visble 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 `mu A` 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 photoelectric current is setup in the circuit whichf is measured using micro ammeter.
The variation of photocurrent with respect to (i) intensity of incident light (ii) the potential difference between the electrodes (iii) the nature of the materaial and (iv) frequency of incident light can be studied with the help of this apparatus.