Question

When a surface is irradiated with light of wavelength $4950\stackrel{o}{A}$, a photoncurrent appears which vanishes if a retarding potential greater than 0.6 V is applied across the photo tube. When a different source of light is used, it is found that the critical retarding potential is changed to 101 V. If the photoelectrons (after emission from the surface) are subjected to a magnetic field of 10 T. The work function of the emitting surface is $3.04\times {10}^{-X}V$. Find X?

Answer 1

Einstein's equation for photoelectric effect is

$\frac{hc}{\lambda }=W+e{V}_0$

$\frac{6.6\times {10}^{-34}\times 3\times {10}^8}{4950\times {10}^{-10}}=W+1.6\times {10}^{-19}\times 0.6$

$W=3.04\times {10}^{-19}V$

hence X = 19