A photoelectric surface is illuminated successively by monochromatic light of wavelength `lambda and lambda/2.` If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface of the material is :
(h = Planck's constant, c = speed of light)

Options

A. `(hc)/lamda`
B. `(2hc)/lamda`
C. `(hc)/(3lamda)`
D. `(hc)/(2lamda)`

Answer

D

Explanation

`K_("max") = (hc)/lamda -phi_0`
`K_1 =(hc)/lamda-phiand K_2 =3K_1 =(2hc)/lamda -phi`
`implies 3K_1 -K_1 - (2hc)/lamda -phi-(hc)/(lamda )+phiimplies phi = (hc)/(2lamda)`