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. 0.5 eV
B. 0.75 eV
C. 1 eV
D. 1.25 eV

Answer

C

Explanation

The frequency (v) is increased by 20%.
But `E=hv" " E_(1)=hv` and `E_(2)=6/5 E_(1)`
From Einstein's equation, `E_(1)=hv=K_(1)+W_(0)=0.5+W_(0)` ...(1)
and in the second case, `E_(2)=6/5E_(1)=0.8+W_(0)` ...(2)
`:.E_(2)-E_(1)=(E_(1))/(5)=0.3" " :.E_(1)=1.5eV` ...(3)
`:.` From(1), `1.5=0.5+W_(0)" " :.W_(0)=1 eV`