Question

If the wavelength of incident light changes from 400 nm to 300 nm, then the stopping potential of photoelectrons emitted from a surface becomes (approximately)

• A. (A) 1.0 V greater
• B. (B) 1.0 V smaller
• C. (C) 0.5 V greater
• D. (D) 0.5 V smaller

Answer 1

Answer: (A)

(A) 1.0 V greater

Answer 2

Explanation:
As the stopping potential is given by:V=hcλe−θeFor the first case, the stopping potential isV1=hcλ1e−ϕeFor the second case, the stopping potential isV2=hcλ2e−θeV2−V1=hcλ2ee−hcλ1e=hce[1λ2−1λ1]V2−V1=6.6×10−34×3×1081.6×10−19×110−9×[1300−1400]V2−V1=6.6×10−34×3×1081.6×10−19×110−9×[11200]=1.03v