Photons of wavelength `lambda` are incident on a metal. The most energetic electrons ejected from the metal are bent into a circular arc of radius R by a perpendicular magnetic field having a magnitude B. The work function of the metal is (Where symbols have their usual meanings) -

Options

A. `(hc)/lamda-m_e+(e^2B^2R^2)/(2m_e)`
B. `(hc)/lamda+2m_e((eBR)/(2m_e))^2`
C. `(hc)/lamda-m_ec^2-(e^2B^2R^2)/(2m_e)`
D. `(hc)/lamda-2m_e((eBR)/(2m_e))^2`

Answer

D

Explanation

`N=(hc)/lamda=W+1/2m((ReB)/m)^2`