When the energy of the incident radiation is increased by 20% ,the kinetic 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

Maximum kinetic energy `(1)/(2)mv_(max)^(2)=hf-phi`
`therefore` In first condition 0.5 eV=hf-`phi`…(1) and
By increasing energy 0.8 eV=1.2 hf-`phi`…..(2)
multiplying equation (1) by 1.2,
0.6 eV=1.2 hf-1.2 `phi`
0.8 eV=1.2 hf-`phi`
`(--+)/(-0.2 eV=-0.2 phi)`
`therefore phi=1.0 eV`