Question

When light of wavelength '`lambda`' is incident on photosensitive surface, photons of power 'P' are emitted. The number of photons (n) emitted in 't' second is (h = Planck's constant, c = velocity of light in vacuum) ____________.

Options

• `("P"lambda"t")/"hc"`

• `"hP"/(lambda"tc")`

• `("P"lambda)/"htc"`

• `"hc"/("P"lambda"t")`

Answer 1

When light of wavelength '`lambda`' is incident on photosensitive surface, photons of power 'P' are emitted. The number of photons (n) emitted in 't' second is `("P"lambda"t")/"hc"`.

Explanation:

Energy of each photon = `"hc"/lambda`

If n photons are emitted in time t then the energy emitted in time t is `"nhc"/lambda`

Power P = Energy emitted per second

`= "nhc"/(lambda"t")`

`therefore "n" = ("P"lambda"t")/"hc"`