Question

`A` light source of power 16 watts emits light of wavelength `310nm`. If all emitted photons are made to strike a metal plate of work function `1.5eV` then find out the magnetic of photo-current if `50%` of incident photons eject photoelectrons.

Answer 1

No. of photons per second from source `=("power")/("energy of photon")=(16J//sec)/((1240)/(310)xx1.6xx10^(-19)J) = 2.5xx10^(19) "photons/sec"`
No. of photoelectron emitted `=(1)/(2)(2.5xx10^(19))` per sec.
`("charge")/("time")` = photoelectron current `=(1)/(2)(2.5xx10^(19))xx1.6xx10^(-19)C//sec = 2` amp