$A$ laser beam is operating at $100 \,mW$. The amount of energy stored by $90 \,cm$ length of this laser beam will be

$A$ $100 \ W$ electric bulb produces electromagnetic radiation with an electric field amplitude of $2 \ V \ m^{-1}$ at a distance of $10 \ m$. Assuming it as a point source, estimate the efficiency of the bulb. (in $\%$)

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.,$\frac{\lambda_A}{\lambda_B}$.

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?

Generation,propagation,and detection of electromagnetic waves is the basis of:

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