A photon of energy E ejects a photoelectron from a metel surface whose work function is `phi_(0)`. If this electron enters into a unifrom magnetic field of induction B in a direction perpendicular to the field and describes a circular path of radius r, then the radius r, is given by, (in the usual notation)

Options

A. `sqrt((2m(E - phi))/(eB))`
B. `sqrt(2m(E - phi)eB)`
C. `sqrt((2e(E - phi))/(mB))`
D. `sqrt((2m(E - phi))/(Be))`

Answer

D

Explanation

`E =phi +K_(max)` `implies K_(max) =E -phi`
`R=(mv)/(Bq) =(sqrt(2m K_(max)))/(Be)`
`=(sqrt(2m (E -phi)))/(Be)`