The maximum KE of photoelectrons emitted from a cetain metallic surface is 30 eV when monochromatic radiation of wavelength `lamda` falls on it. When the same surface is illuminated with light of wavelength `2lamda`, the minimum KE of photoelectrons is found to be 10 eV. (a) Calculate the wavelength `lamda` and (b) determine the maximum wavelength of incident radiation for which photoelectric emission is possible.

Answer

`310.3 Å, 1249Å`

Explanation

`K_(1)=30 eV =30xx1.6xx10^(-19)J`,
`K_(2)=10 eV=10xx1.6xx10^(-19)J`,
Use, `K=(hc)/lambda-phi_(0)`, for two cases and solve the same of `lambda and phi_(0) Use, lambda_(0)=hc//phi_(0)`