$5 \%$ 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 .......... $W/m^2$.

$A$ microwave and an ultrasonic sound wave have the same wavelength. Their frequencies are in the ratio (approximately):

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?

The electric field of a plane electromagnetic wave is given by $\overrightarrow{E} = E_{0} \frac{\hat{i}+\hat{j}}{\sqrt{2}} \cos (kz+\omega t)$. At $t=0$,a positively charged particle is at the point $(x, y, z) = (0, 0, \frac{\pi}{k})$. If its instantaneous velocity at $t=0$ is $v_{0} \hat{k}$,the force acting on it due to the wave is

The graph between radiation power $P$ from a linear antenna and the square of the length of the antenna $l^2$ is shown in the figure for two antennas $A$ and $B$. If all other parameters are the same,find the ratio of the wavelengths of $A$ and $B$,i.e.,$\frac{\lambda_A}{\lambda_B}$.

The electric field intensity produced by the radiation coming from a $100 \, W$ bulb at a distance of $3 \, m$ is $E$. The electric field intensity produced by the radiation coming from a $60 \, W$ bulb at the same distance is $\sqrt{\frac{x}{5}} E$. The value of $x$ is ......... .