Question

Light of wavelength λ, 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 ______.

Options

• increase

• decrease

• be zero

• become exactly half

Answer 1

Light of wavelength λ, 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 increase.

Explanation:

According to Einstein's photoelectric equation, `"hc"/lambda` = Φ + E

Here

E = kinetic energy

Φ = work function

If E is constant, then `1/lambda` ∝ Φ

∴ If wavelength λ is decreased, then stopping potential Φ will increase such that `"hc"/lambda` = Φ = constant.