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11. Dual nature of radiation and matter — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics11. Dual nature of radiation and matter1 Mark
MCQ
Ultraviolet radiations of $6.2\,eV$ falls on an aluminium surface (work function $4.2\;eV$). 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.
$3.2 \times {10^{ - 19}}$
b
(b) ${K_{\max }}(eV) = E\,(eV) - {W_0}\,(eV)$$ = 6.2 - 4.2 = 2\;eV$

$\therefore \,\,\,\,\,{K_{\max }}(Joules) = $$2 \times 1.6 \times {10^{ - 19}}J = 3.2 \times {10^{ - 19}}J$

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