Question

The threshold frequency for a metallic surface corresponds to an energy of 6.2 eV, and the stopping potential for a radiation incident on this surface is 5V. The incident radiation lies in-

• A. X-ray region
• B. Ultraviolet region
• C. Infrared region
• D. Visible region

Answer 1

Answer: (B)

Ultraviolet region

Answer 2

E = φ + eV₀

E = 6.2 eV + 5eV = 11.2 eV

λ = $\frac { 12420 } { 11.2 }$ = 1108 . 9eV

Which lies in U.V. region.