Q. Ultraviolet radiation of 6.2eV falls on an aluminium surface (work function 4.2eV). The kinetic energy in joule of the fastest electron emitted is approximately
A) $3 \times 10^{- 21}$
B) $3.2 \times 10^{- 19}$
C) $3 \times 10^{- 17}$
D) $3 \times 10^{- 15}$
Explanation
(b) $E_{k} = E - \phi_{0} = 6.2 - 4.2 = 2.0eV$
$= 2.0 \times 1.6 \times 10^{- 19} = 3.2 \times 10^{- 19}$ J
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.