A beam of electromagnetic radiation of intensity `12.8 xx 10^(-5) W//cm^(2)` is comprised of wavelength, `lambda = 155 nm` . It falls normally on a metal (work function `phi = 2eV`) of surfacce area of the ` 1 cm^(2)`. If one in `10^(3)` photons ejects total number of electrons ejected in 1 s in `10^(x)`. (hc = 1240 eVnm) `1eV = 1.6 xx 10^(-19)`J =, then x is _____.

Answer

A

Explanation

No. of photons incident in 1 sec.
`N=(IA)/(((hc)/(lamda)))=(PC.A)/((hc)/(lamda))` where P is pressure.
`=(3.2xx10^(-13)xx3xx10^(8)xx1)/(((1240)/(620))xx1.6xx10^(-19))=3xx10^(14)`
`therefore` No. of electrons ejected are `(3xx10^(14))/(3xx10^(3))=10^(11)`