Ultraviolet radiations of 6.2 eV falls on an aluminium surface (w… - Vidyadip

MCQ

Ultraviolet radiations of $6.2 \mathrm{eV}$ falls on an aluminium surface (work function $4.2 \mathrm{eV}$ ). The kinetic energy in joules of the fastest electron emitted is approximately

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

✓

Answer

Correct option: B.

$3.2 \times 10^{-19}$

$ K_{\max }(\mathrm{eV})=E(\mathrm{eV})-W_0(\mathrm{eV})=6.2-4.2=2 \mathrm{eV} $
$ \therefore K_{\max }(\text { Joules })=2 \times 1.6 \times 10^{-19} \mathrm{~J}=3.2 \times 10^{-19} \mathrm{~J}$

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