When the energy of the incident radiation is increased by `20 %` , kinetic energy of the photoelectrons emitted from a metal surface increased from `0.5 eV to 0.8 eV`. The work function of the metal is

Options

A. 0.65 eV
B. 1.0 eV
C. 1.3 eV
D. 1.5 eV

Answer

B

Explanation

`E=phi+K.E._(max)`
`hv=phi+0.5" "...(i)`
Now, `1.2hv = phi + 0.8 " "...(ii)`
Subtract (i) from (ii)
`0.2 hv = 0.3`
`hv = 3//2`
`hv =1.5`
Substituting equation (i)
`1.5=phi+0.5`
`phi=1 eV`