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 $3 \times 10^{7} \, ms ^{-1}$. 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. $12.8 \times 10^{-17} \,N$
• D. $12.8 \times 10^{-18}\, N$

Answer 1

Answer: (D)

$\frac{ E _{0}}{ C }= B _{0}$
$F _{\max }= eB _{0} \,V$
$=1.6 \times 10^{-19} \times \frac{800}{3 \times 10^{8}} \times 3 \times 10^{7}$
$=12.8 \times 10^{-18} \,N$