A silver of radius `4.8 cm` is suspended by a thread in the vacuum chamber . `UV` light of wavelength `200 nm` is incident on the ball for some times during which a total energy of `1 xx 10^(-7) J` falls on the surface . Assuming on an average one out of `103` photons incident is able to eject electron. The potential on sphere will be

Options

A. `1 V`
B. ` 2 V`
C. `3 V`
D. Zero

Answer

C

Explanation

`n = (E lambda)/( hc) = ( 1 xx 10^(-7) xx 200 xx 10^(-9))/(6.6 xx 10^(-34) xx 3 xx 10^(8)) = 1 xx 10^(11)`
Number of electrons ejected ` = (10^(11))/(10^(3)) = 10^(8)`
`:. V = (q)/( 4 pi epsilon_(0) r) = ((10^(8) xx 1.6 xx 10^(-19)) xx 9 xx 10^(9))/(4.8 xx 10^(-2)) = 3 V`