Electromagnetic Waves · JEE Main previous year questions

2021 2 questions

1. Q332021 · 18 Mar 2021 · Shift 1

   A plane electromagnetic wave of frequency 100 MHz is travelling in vacuum along the x-direction. At a particular point in space and time, $\vec{B}=2.0\times 10^{-8}\hat{k}T$. (where, $\hat{k}$ is unit vector along z-direction) What is $\vec{E}$ at this point?

   1. A.$0.6\hat{j}\text{ V/m}$
   2. B.$6.0\hat{k}\text{ V/m}$
   3. C.$6.0\hat{j}\text{ V/m}$
   4. D.$0.6\hat{k}\text{ V/m}$
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   Answer: C

2. Q432021 · 16 Mar 2021 · Shift 1

   For an electromagnetic wave travelling in free space, the relation between average energy densities due to electric (${\mathrm{U}}_{\mathrm{e}}$) and magnetic (${\mathrm{U}}_{\mathrm{m}}$) fields is :

   1. A.${\mathrm{U}}_{\mathrm{e}}={\mathrm{U}}_{\mathrm{m}}$
   2. B.${\mathrm{U}}_{\mathrm{e}}\ne {\mathrm{U}}_{\mathrm{m}}$
   3. C.${\mathrm{U}}_{\mathrm{e}}<{\mathrm{U}}_{\mathrm{m}}$
   4. D.${\mathrm{U}}_{\mathrm{e}}>{\mathrm{U}}_{\mathrm{m}}$
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   Answer: A