When light of wavelength λ is incident on photosensitive surface, the stopping potential is V . When light of wavelength 3 λ is incident on same surface, the stopping potential is V 6 . Threshold wavelength for the surface is

Step-by-step solution

Using h c λ - ϕ = e V When, wavelength λ is incident on metallic surface, the sopping potential required to stop most energetic electron is V and when wavelength increases to 3 λ , stopping potential required as V 6 ∴ h c λ = e V + ϕ ..... (i) And h c 3 λ = e V 6 + ϕ .... (ii) Thus equation (ii) can be rewritten as 2 h c λ = e V + 6 ϕ ..... (iii) Subtracting equation (i) from (iii) we get h c λ = 5 ϕ and ϕ = h c λ 0 Thus λ 0 = 5 λ