In an experimental set up to study the photoelectric effect a point...

In an experimental set up to study the photoelectric effect a point source of light of power 3.2 mW is used. The source emits mono energetic photons of energy 5 eV and is located at a distance

\mathrm{d}=0.8 \mathrm{~m}

from centre of a stationary metallic sphere of work function

\mathrm{W}=3.0 \mathrm{eV}

. The radius of the sphere is

\mathrm{R}=8 \mathrm{~mm}

. Assume that the sphere is isolated and photo electrons are instantly swept away after emission. Also assume that the efficiency of photoelectric emission is one for every

10^6

photons. In the present set up

Options

AThe de Broglie wave length of fastest moving photoelectron is nearly $8.7 \mathrm{~A}^0$
BIt is observed that after some time emission of photoelectrons from the surface of metal sphere is stopped, the charge on sphere just when the electron emission stops is $64 \pi \epsilon_0 \times 10^{-3} \mathrm{C}$
CTime after which photo electric emission stops is nearly 111 s
DThe light source emits $4 \times 10^{15}$ photons per sec

Correct answer

D. The light source emits $4 \times 10^{15}$ photons per sec

Step-by-step solution

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