(a) Calculate `KE` of photoelectron emiited from sodium surface when light of wavelength `400nm` is incident on it (Work function of sodium `=2.28eV`).
(b) Calculate maximum wavelength (threshold wavelength) that can cause emission of photoelectron from sodim surface.

Explanation

(a)`hupsilon = hupsilon_(0) + KE` where `hupsilon_(0)=phi=2.28eV`
`impliesKE=hupsilon-hupsilon_(0)=-2.28eV+(1240)/(400)eV=0.82eV`
(b) For max `lambda, KE =0`
`implies (hc)/(lambda_(max))=phiimplies(1240)/(lambda_(max))=2.28`
`lambda_(max) =544nm`