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.

Options

A. `(5)/(4)`
B. `(9)/(5)`
C. `(9)/(4)`
D. `(9)/(2)`

Answer

D

Explanation

For maxiumum photocurrent the combination is as follows
(a) 2 watt `rArr 4xx10^(18)` photons/sec. ltbgt (b) 3 watt `rArr 5xx10^(18)` photons/sec.
(c) 5 watt `rArr 9xx10^(18)` photons /sec.
photoelectrons will be emitted from comcination (a),(b)and(c) all
`therefore` Photocurrent =`(4+5+9)xx10^(18)xx1.6xx10^(-19)` Amp
=2.88
` therefore` Ratio`=(92.88)/(0.64)=4.5(18)/(4)rArr(9)/(2) `