Question

The difference between threshold wavelengths for two metal surfaces A and B having work function Φ_A = 9 eV and  Φ_B = 4.5 eV in nm is ______.

(Given, hc = 1242 eV nm)

Options

• 264

• 138

• 276

• 540

Answer 1

The difference between threshold wavelengths for two metal surfaces A and B having work function Φ_A = 9 eV and  Φ_B = 4.5 eV in nm is 138.

Explanation:

Given: Φ_A = 9 eV

Φ_B = 4.5 eV

Threshold wavelength (λ₀) = `(hc)/Phi`

For metal A:

λ_A = `1242/9`

= 138 nm

For metal A:

λ_B = `1242/4.5`

= 276 nm

Δλ = λ_B​ − λ_A​

= 276 − 138

= 138 nm