In a plane EM wave, the electric field oscillates sinusoidally at a frequency of 30 MHz and amplitude $150 \mathrm{~V} / \mathrm{m}$, Identify the correct expression of $\mathbf{B}$ assuming the wave is propagating along $X$-axis and is oscillating along $Y$-axis.

On a particular day, the sun delivers an average power of $\left(\frac{6}{\pi} \times 10^3\right) \frac{\mathrm{W}}{\mathrm{m}^2}$ to the top of earth's atmosphere. Find the amplitude of magnetic field for the electromagnetic waves above atmosphere.

(Take, $\mu_0=4 \pi \times 10^{-7}$ SI unit)

A laser beam has intensity $2.1 \times 10^{15} \mathrm{~W} / \mathrm{m}^2$. The amplitude of magnetic field in the beam in approximately is

About $20 \%$ of the power of a 100 W bulb is converted to visible radiation. Assuming that the radiation is emitted isotropically and neglecting reflection, the average intensity of visible radiation at a distance of 5 m is $\frac{\alpha}{25 \pi} \mathrm{~W} / \mathrm{m}^2$. The value of $\alpha$ is