A light of wavelengt `1240Å` falls on a metallic sphere of radius 1 m and work function `W_(0) = 3eV` . The maximum number of electron left from the sphere till photoelectric effest stops will be- (approximately)

Options

A. `5xx10^(6)`
B. `5 xx 10^(7)`
C. `5 xx 10^(9)`
D. `5 xx 10^(12)`

Answer

3

Explanation

Photoelectric effect stop when
`V_("stop") =(K"ne")/(R)`
from photo electric `eq^(n)`
`(hc)/(lambda) - W_(0) =1//2 mV_("max")^(2)`
`(hc)/(lambda) - W_(0) = eV_("stop")`
`(hc)/(lambda) - W_(0) = c (K("ne"))/(R)`
`therefore n= ((hc)/(lambda) - W_(0))`
`(R)/(Ke^(2))`
`=((12400)/(1240)-3)xx (1.6 xx 10^(-19))/((1.6 xx 10^(-19))^(2)) xx (1)/(9xx 10^(9))`
`= 5 xx 10^(9)`