Question

The number of photons falling per second on a completely darkened plate to produce a force of 6.62 x 10^-5 N is 'n'. If the wavelength of the light falling is 5 x 10^-7 m, then n = ____________ x 10²². (h = 6.62 x 10^-34 J-s)

Options

• 1

• 5

• 0.2

• 3.3

Answer 1

The number of photons falling per second on a completely darkened plate to produce a force of 6.62 x 10^-5 N is 'n'. If the wavelength of the light falling is 5 x 10^-7 m, then n = 5 x 10²².

Explanation:

`"P" = "n"/"t"  "hc"/lambda`

But P = Fc

`therefore "Fc" = "n"/"t" "hc"/lambda`

`therefore "n"/"t" = ("F"lambda)/"h" = (6.62 xx 10^-5 xx 5 xx 10^-7)/(6.62 xx 10^-34)`

` = 5 xx 10^22`