A light beam is described by

Question:

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 $3 \times 10^{7}$ $\mathrm{ms}^{-1}$. What is the maximum magnetic force exerted on the electron?

 

  1. $1.28 \times 10^{-18} \mathrm{~N}$

  2. $1.28 \times 10^{-21} \mathrm{~N}$

  3. $12.8 \times 10^{-17} \mathrm{~N}$

  4. $12.8 \times 10^{-18} \mathrm{~N}$


Correct Option: , 4

Solution:

$\frac{\mathrm{E}_{0}}{\mathrm{C}}=\mathrm{B}_{0}$

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

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

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

Ans. 4

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