Radiation of wavelength 180 nm eject photoelectrons from a plate whose work function is 2.0 eV. If a uniform magnetic field of flux density `5.0xx10^(-5)T` is applied parallel to plate, what should be the radius of the path followed by electrons ejected normally from the plate with maximum energy:

Options

A. 0.074 m
B. 0.592 m
C. 0. 419 m
D. 0. 144 m

Answer

D

Explanation

`E=hv-w=(hc)/(lambda)-w`
Here `, lambda=180 nm=180xx10&^(-9)m`
`w=2.0eV=2.0xx1.6xx10^(-9)J`
`:.E=7.8xx10^(-19)J`
Also `(1)/(2)mv^(2)=E:. V= sqrt((2E)/(m))`
so `v=sqrt((2xx7.8xx10^(-19))/(9.1xx10^(-31)))=1.31xx10^(6)m//s`
Radius r in a magnetic field in induction B is given
`Bev=(mv^(2))/(r) or r=(mv)/(eB)`
Using `B=5xx10^(-5)T`
Then `r=0.149 m`