On a photosensitive material, when frequency of incident radiation is increased by 30% kinetic energy of emitted photoelectrons increases from `0.4 eV` to `0.9 eV`. The work function of the surface is

Options

A. 1 eV
B. 1.267 eV
C. 1.4 eV
D. 1.8 eV

Answer

B

Explanation

From Einstein's photoelectric equations
`hv=W_(0)+1/2 mv^(2)`
`:.hv=W_(0)+0.4` ...(1)
and when v is increased by 30%
i.e. it becomes 1.3 `hv=W_(0)+0.9` ...(2)
Multiplying (1) by 1.3, we get
`1.3hv=1.3W_(0)+1.3xx0.4` ...(3)
From (2) and (3), we get
`1.3W_(0)+0.52=W_(0)+0.9`
`0.3W_(0)=0.9-0.52=0.38`
`:.W_(0)=(0.38)/(0.3)=1.267 eV` ...Option (b)