Question

A beam of light travelling along $x$-axis is described by the electric field $E _{ y }=\left(600\, Vm ^{-1}\right) \sin \omega( t - x / c )$ then maximum magnetic force on a charge. $q =2^{ e }$, moving along $y$-axis with a speed of $3.0 \times 10^{7}\, ms ^{-1}$ is $\left(e=1.6 \times 10^{-19} \,C \right)$

• A. $ 19.2\times 10^{-17}\,N $
• B. $ 1.92\times 10^{-17}\,N $
• C. $0.192 \,N$
• D. none of these

Answer 1

Answer: (B)

Maximum magnetic field is given by
$B_{0}=\frac{E_{0}}{c}$
Here, $E_{0}=600\, Vm ^{-1} $
$c=3 \times 10^{8} \,m / s$
$\therefore B_{0}=\frac{600}{3 \times 10^{8}} $
$=2 \times 10^{-6} \,T$
Maximum magnetic force imposed on given charge is
$F_{m}=q v B_{0}=2\, e v B_{0}$
$=2 \times 1.6 \times 10^{-19} \times 3 \times 10^{7} \times 2 \times 10^{-6}$
$=1.92 \times 10^{-17}\, N$