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8. Electromagnetic waves — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics8. Electromagnetic waves1 Mark
MCQ
A light beam is described by $E=800 \sin \omega\left(t-\frac{x}{c}\right)$

An electron is allowed to move normal to the propagation of light beam with a speed of $3 \times 10^{7}\;{ms}^{-1}$. What is the maximum magnetic force exerted on the electron ?

  • A
    $1.28 \times 10^{-18}\, {N}$
  • B
    $1.28 \times 10^{-21}\, {N}$
  • C
    $12.8 \times 10^{-17} \,{N}$
  • ✓
    $12.8 \times 10^{-18} \,{N}$
✓

Answer

Correct option: D.
$12.8 \times 10^{-18} \,{N}$
d
$\frac{{E}_{0}}{{C}}={B}_{0}$

${F}_{\max }={eB}_{0} {V}$

$=1.6 \times 10^{-19} \times \frac{800}{3 \times 10^{8}} \times 3 \times 10^{7}$

$=12.8 \times 10^{-18}\, {N}$

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