(i) To ensure that all the electrons emitted by the cathode reach the anode to maximize the photo current.
(ii) To limit control or lower the current in the circuit.
(iii) The energy of the incident light must be greater than work function of the cathode surface if photo electron emission has to occur.
(iv) The current flowing in the circuit ensures that the relay switch is attracted to the electromagnet.
When UV light is cut-off, the photo current ceases and the relay switch completes the burglar alarm circuit and the alarm sounds.
sharon kalunda answered the question on September 6, 2019 at 08:53
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