Question

When a certain metallic surface is illuminated with monochromatic light of wavelength λ, the stopping potential for photoelectric current is 3V₀ and when the same surface is illuminated with light of wavelength 2λ, the stopping potential is V₀. The threshold wavelength of this surface for photoelectric effect is-

• A. 6λ
• B. 4λ/3
• C. 4λ
• D. 8λ

Answer 1

Answer: (C)

4λ

Answer 2

$\frac { \mathrm { hc } } { \lambda } - \frac { \mathrm { hc } } { \lambda _ { 0 } }$ = e(3V₀) …(1)

= eV₀ ...(2)

$\frac { \frac { \mathrm { hc } } { \lambda } - \frac { \mathrm { hc } } { \lambda _ { 0 } } } { \frac { \mathrm { hc } } { 2 \lambda } - \frac { \mathrm { hc } } { \lambda _ { 0 } } } = \frac { 3 } { 1 }$

λ₀ = 4λ