Photons absorbed in matter are converted to heat.A source emitting n photon /sec of frequency v is used to convert 1 kg of ice at 0 `""^(@)C` to water at 0`""^(@)C`.Then the time T taken for the conversion

Options

A. decreases with increasing n,with v fixed.
B. decreases with n fixed ,v increasing
C. remiains constant with n and v changing such that nv=constant.
D. Increases when the product nv increases.

Answer

A, B, C

Explanation

Power of given source,
`P=(E_(n))/(t)=(n.hv)/(t)=((n.)/(t))hv`
`therefore` P=nhv (`because` Here `(n.)/(t)`=no. of photons)
emitted per unit time =n(given)
Energy obtained by given amount of ice in time T,E.=PT
`therefore` mL=(nhv)T(From equation (1))
L=latent heat of fusion of ice)
`therefore T=(mL)/(nhv)`
`therefore Tprop(1)/(nv)` (`beacuse` m,L,h are constant).....(2)
From equation (2),
(i)If v=constant then by increasing n,T will decrease.
`implies` Option (A) is correct.
(ii)If n =constant then by increasing v,T will decrease
`implies`Option (B) is correct .
(iii)If nv=constant then T=constant.
`impliesOption (C) is correct.