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

According to Einstein's equation,
`E = hf - W_(0) or, hf = E + W_(0)`
For the first case, `hf_(1) = E_(1) + W_(0)`
For the second case, `hf_(2) = E_(2) + W_(0)`
`:. (hf_(2))/(hf_(1)) = (E_(2) + W_(0))/(E_(1) + W_(0)) or, (120)/(100) = (0.8 + W_(0))/(0.5 + W_(0))`
or, `3 + 6W_(0) = 4 + 5W_(0)`
`:. W_(0) = 1eV`