Question

Light of wavelength A which is less than threshold wavelength is incident on a photosensitive material. If incident wavelength is decreased so that emitted photoelectrons are moving with same velocity, then stopping potential will
A. increase
B. decrease
C. be zero
D. become exactly half

Answer 1

Correct Answer - A
According to photoelectric equation,
`(hc)/lambda = phi+E`
Symbols have their usual meaning
E =kinetic energy
If E is constant, then `1/lambda alpha phi=`
If we decrease the wavelength lambda, then stopping potential `phi` will increase such that `(hc)/lambda-phi` = constant