The energies required to set up in a cube of side $10 \ cm$,$(a)$ a uniform electric field of $10^7 \ V \ m^{-1}$ and $(b)$ a uniform magnetic field of $0.25 \ Wb \ m^{-2}$,are respectively about $(\mu_0 = 4\pi \times 10^{-7} \ H \ m^{-1}, \epsilon_0 = 8.9 \times 10^{-12} \ F \ m^{-1})$.

The power radiated from a linear antenna of length $l$ is proportional to (Given,$\lambda =$ wavelength of the wave):

$A$ radar sends an electromagnetic signal with an electric field $E_{0} = 2.25\,V/m$ and a magnetic field $B_{0} = 1.5 \times 10^{-8}\,T$,which strikes a target on the line of sight at a distance of $3\,km$ in a medium. After that,a part of the signal (echo) reflects back towards the radar with the same velocity and along the same path. If the signal was transmitted at time $t_{0}$ from the radar,then after how much time (in $\times 10^{-5}\,s$) will the echo reach the radar?

Consider three quantities $x = E/B$,$y = \sqrt{1/(\mu_0 \varepsilon_0)}$ and $z = l/RC$. Here,$l$ is the length of a wire,$C$ is capacitance,and $R$ is resistance. All other symbols have standard meanings. Which of the following statements is correct?

$5 \%$ of the power of a $100 \, W$ bulb is converted to visible radiation. The average intensity of visible radiation at a distance of $10 \, m$ from the bulb is .......... $W/m^2$.

In an electromagnetic wave,the electric field and magnetising field are $100\,V\,m^{-1}$ and $0.265\,A\,m^{-1}$ respectively. The maximum energy flow is.......$W\,m^{-2}$.