Three laser guns labelled as I,II&III have power 2 watt, 3watt and 5 watt (not necessarily in same
order) are used to produce photocurrent from nmental plate as show in diagram. Number of photons
emitted by laser guns are `4xx10^(18),5xx10^(18)` and `9xx10^(18)` per sec. metal plante have thershold energy `4.5`
`xx10^(-19) J`. Neither the power nor the number of photon emitted b a particlar laser gun is known and
it is know that call all capable emits a photonelectron.

Minimum photocurrent which must be passed thought the circuit.

Options

A. 2.88
B. 1.44
C. 2.08
D. 0.64

Answer

D

Explanation

For minnimum photocurrenth the combination is follows is as follows
(a) `2 wattrArr 5xx10^(18)` photons/sec. ltbgt (b) `3 wattrArr 9xx10^(18)` photons/sec.
(c) `5 watt rArr 4xx10^(18)` photons /sec.
Combination (a) &(b) does not given any photoelectron only combination (c) will produce
[photoelectron .
`therefore` photocurrent =`4xx10^(18)xx1.6xx10^(-19)` Amp.
` =0.64` Amp.