Question

Photoelectrons are emitted from a photosensitive surface for the light of wavelengths λ₁ = 360 nm and λ₂ = 600 nm. What is the ratio of work functions for lights of wavelength 'λ₁' to 'λ₂'?

Options

• 6 : 1

• 3 : 5

• 5 : 3

• 1 : 6

Answer 1

5 : 3

Explanation:

`"hc"/lambda_1 - phi_1` = KE   λ₁ = 360 nm = 360 × 10^-9 m

`"hc"/lambda_2 - phi_2` = KE   λ₂ = 600 nm = 600 × 10^-9 m

`"hc"/lambda_1 - phi_1    phi prop 1/lambda` 

`therefore phi_1/phi_2 = lambda_2/lambda_1 = 600/360 = 10/6 = 5/3`