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Photons absorbed in the matter are converted to heat. A source emitting n photon/sec of frequency ν is used to convert 1kg of ice at 0°C to water at 0°C. Then, the time T taken for the conversion

(a) decreases with increasing n, with ν fixed

(b) decreases with n fixed, ν increasing

(c) remains constant with n and ν changing such that nν = constant

(d) increases when the product nν increases

Answers (1)

The answer is the option (a, b. c).

Heat energy required to convert 1Kg of ice at 0^{\circ} C to water at 0^{\circ} C is E=mL

 If n is the number of photons incident per second and time t is taken by radiation to 

melt the ice at 0^{\circ}C. 

Then E=n hv t 

t=\frac{mL}{nhv}\\

  Or t\alpha \frac{1}{nv}\\

[m, L and h are constants ] Hence, (a), (b) and (c) are correct.

If nv increases then T decreases ;so (d) isn't correct.
 

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