When a surface is irradiated with light of wavelength 4950oA, 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 3.04×10−XV. Find X?
Einstein's equation for photoelectric effect is
hcλ=W+eV0
6.6×10−34×3×1084950×10−10=W+1.6×10−19×0.6
W=3.04×10−19V
hence X = 19