Threshold wavelength for photoelectric effect on sodium is `5000 Å` . Its work function is

Options

A. `15 J`
B. `16 xx 10^(-14) J`
C. `4 xx 10^(-19) J`
D. `4 xx 10^(-81) J`

Answer

C

Explanation

`W_(0) = (hc)/(lambda_(0)) = (6.625 xx 10^(-34) xx 3 xx 10^(8))/( 5000 xx 10^(-10)) J = 4 xx 10^(-19) J`