• # question_answer The magnetic field of a plane electromagnetic wave is given by : $\vec{B}={{B}_{0}}\hat{i}[cos(kz-\omega t)]+{{B}_{1}}\hat{j}\cos (kz+\omega t)$ where ${{B}_{0}}=3\times {{10}^{-5}}T$ and ${{B}_{1}}=2\times {{10}^{-6}}T.$ The rms  value of the force experienced by a stationary charge $Q={{10}^{-4}}C$at $z=0$is closest to :             [JEE Main 9-4-2019 Morning] A) $0.9\text{ }N$                       B) $0.1\text{ }N$C) $3\times {{10}^{2}}N$                  D) $0.6N$

Maximum Electric field E = ${{\vec{E}}_{0}}=(3\times {{10}^{-5}})c\left( -\hat{j} \right)$ ${{\vec{E}}_{1}}=(2\times {{10}^{-6}})c\left( -\hat{i} \right)$ Maximum force ${{\vec{F}}_{net}}=q\vec{E}=qc\left( -3\times {{10}^{-5}}\hat{j}-2\times {{10}^{-6}}\hat{i} \right)$ ${{\vec{F}}_{0\max }}={{10}^{-4}}\times 3\times {{10}^{8}}\sqrt{{{(3\times {{10}^{-5}})}^{2}}+{{(2\times {{10}^{-6}})}^{2}}}$$=0.9N$ ${{F}_{rms}}=\frac{{{F}_{0}}}{\sqrt{2}}=0.6N$                     (approx) Option