Physics

Problem

A metal surface has threshold wavelength

\lambda_0 = 550\,\text{nm}

. Three monochromatic beams are incident on it separately: (i)

\lambda_1 = 400\,\text{nm}

(ii)

\lambda_2 = 550\,\text{nm}

(iii)

\lambda_3 = 650\,\text{nm}

Identify for each beam whether photoelectric emission will take place. Give a brief reason in each case.