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 than in the first case , the work function of the surface of the material is
(`h` = Plank's constant , `c` = speed of light )

Options

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

Answer

B

Explanation

Here, `K_(1)=(hc)/lambda-phi_(0)......(i)`
`K_(2)=3K_(1)=(2hc)/lambda-phi_(0)........(ii)`
Dividing (i) and (ii)
`1/3=((hc)/lambda-phi_(0))/((2hc)/lambda-phi_(0)) or (2hc)/lambda-phi_(0)=(3hc)/lambda-3phi_(0)`
or `2phi_(0)=(hc)/lambda or phi_(0)=(hc)/(2lambda)`