Question

if the wavelength of incident light changes from 400nm to 300 nm the stopping potential for photoelectrons emitted from a surface becomes approximately
A) 1V greater
B) 1 smaller
C) 0.5 greater
D) 0.5 smaller​

Answer 1

Answer:

E2 - E1 = h f2 - h f1     where f = frequency = c / y     y = wavelength

E2 - E1 = h c ( 1 / y2 - 1 / y1)

E2 - E1 = 6.3 * 10^-34 * 3 * 10^8 / 1 * 10^-7 * (1/3 - 1/4)

E2 - E1 = 2 * 10^-18 * (.33 - .25) = 1.6 * 10E-19 = 1 eV

So the electrons would have an energy greater by 1 eV

requiring an additional stopping potential of 1 V