In a photocell bi chromatic light of wave length `2480 A^(0) ` and `6000 Aoverset(0)` are incident on a cathode whose work function is `4.8eV`.If a uniform magnetic field of `3xx10^(-5) T` exists parallel to the plate, find the radius of the circular path described by the photoelectron. (mass of electron is `9xx10^(-31)kg`)

Answer

4

Explanation

`E_(1)=(12400)/(lambda_(1))=(12400)/(2480)=5eV`
`E_(2)=(12400)/(lambda_(2))=(12400)/(6000) = 2.06eV`
`As E_(2)ltW_(0)andE_(1)gtW_(0)` photo electric emission is possible only with `lambda_(1)`.
Maximum K.E of emitted photo electrons
`K = E_(1)-W_(0) = 0.2eV`.
Photo electrons experience magnetic force and move along a circular path of radius
`r=(mv)/(Bq)=(sqrt(2mk))/(Bq)=rArrr=5cm.`