Correct Answer - C
`:. q=ne = 8piepsilon_0r
`:. n= (8piepsilon_0r)/(e )`
`=(2xx8xx10)^(-3)/(9xx10^9xx1.6xx10^(-19)`
`=1.11x10^7`
Number of photons incident
on sphere per second,
`N_2 = ((N_1)/(4piR^2))(pir^2)`
`=(N_1)/(4R)^2 r^2`
`=((4xx10^(15)(8xx10^(-3))^2/(4(0.8)^2`
`=10^11`
Number of photoelectrons emitted per second,
`N_3 = (N_2)/(10^6) = 10^5`
Now, N_3t = n
`:. t =(n)/(N_3) = 111 s`.