Question

When radiation of wavelength lambda is incident on a metallic surface?

Answer 1

let threshold wavelength be λo.  Ans work function be Φ.

so, eV0 = hc/λ – Φ            ….....  (1)

eV0/4 = hc/2λ – Φ             …........ (2)  

on dividing we get , hc/λ – Φ = 2hc/λ – 4Φ  

=> 3Φ=hc/λ

=> Φ = hc/3λ …       so λ0=3λ.

Hence 3λ is the threshold wavelenght ..

Answer 2

Answer:-

When radiation of wavelength. is incident on a metallic surface, the stopping potential is 4.8 volts. If the same surface is illuminated with radiation of double the wavelength, then the stopping potential becomes 1.6 volts.