Question

Ultraviolet radiation of 6.2 eV falls on an aluminium surface (work function 4.2 eV). The kinetic energy in joule of the fastest electron emitted is approximately

• A. $ 3.2\times {{10}^{-21}} $
• B. $ 3.2\times {{10}^{-19}} $
• C. $ 3.2\times {{10}^{-17}} $
• D. $ 3.2\times {{10}^{-15}} $

Answer 1

Answer: (B)

$ {{K}_{\max }}(eV)=E(eV)-{{W}_{0}}(eV) $
$ =6.2-4.2=2eV $
$ \therefore $ $ {{K}_{\max }}(J)=2\times 1.6\times {{10}^{19}}J $
$ =3.2\times {{10}^{-19}}J $