JEE Main20202 Sep 2020Morning ShiftPhysicsDual Nature of MatterActual
When radiation of wavelength A is used to illuminate a metallic surface, the stopping potential is V . When the same surface is illuminated with radiation of wavelength 3 A , the stopping potential is V 4 . If the threshold wavelength for the metallic surface is nλ then value of n will be :
Correct answer
9
Step-by-step solution
h c λ = ϕ + e V ...........(1) h c 3 λ = ϕ + e V 4 ---------(2) from (1) & (2) h c λ 1 - 1 3 = 3 4 e v hc λ 2 3 = 3 4 eV eV = 8 9 hc λ h c λ = ϕ + 8 9 h c λ ϕ = hc 9 λ = hc λ th λ t h = 9 λ ∴ k = 9