Question

On a photosensitive material when frequency of incident radiation is increased by 30%, kinetic energy of emitted photoelectrons increases from 0.4 eV. The work function of the surface is ______.

Options

• 1 eV.

• 1.267 eV

• 1.4 eV

• 1.8 eV

Answer 1

On a photosensitive material when frequency of incident radiation is increased by 30%, kinetic energy of emitted photoelectrons increases from 0.4 eV. The work function of the surface is 1.267 eV.

Explanation:

According to the Einstein's photoelectric equation,

KE_max = hv₀ - Φ₀

Initially, hv = 0.4 + Φ₀           ... (i)

and when the frequency of incident radiation is increased by 30% then

1.3 hv = 0.9 + Φ₀            ... (ii)

From eqs. (i) and (ii)

0.3Φ₀ = 0.9 - 1.3(0.4)

∴ Φ₀ = `0.38/0.3`

= 1.267 eV