Electromagnetic Waves - Electromagnetism - Physics Previous Year Questions

A beam of white light is incident normally on a plane surface absorbing 70\% of the light and reflecting the rest. If the incident beam carries 10 W of power, the force exerted by it on the surface is

An electromagnetic wave has its electric and magnetic fields given by

$$\mathbf{E}(t)=\mathbf{E}_m \sin (k x-\omega t) ; \quad \mathbf{B}(t)=\mathbf{B}_m \sin (k x-\omega t)$$

If the direction of $\mathbf{E}_m$ and $\mathbf{B}_m$ are in the direction of $(\hat{\mathbf{i}}+\hat{\mathbf{j}})$ and $(\hat{\mathbf{i}}-\hat{\mathbf{j}})$ respectively, the unit vector that gives the direction of propagation of the wave is

An electromagnetic wave is propagating in vacuum along $-\hat{\mathbf{j}}$ direction. The magnetic field of the wave is given by $\mathbf{B}=\left(2 \times 10^{-8}\right) \cos \left[\pi \times 10^{15}\left(t+\frac{y}{c}\right)\right] \hat{\mathbf{k}} \mathrm{T}$. The electric field $\mathbf{E}$ of this wave is ( $c \equiv$ speed of light)

The correct statement among the following is

The speed of electromagnetic waves in a medium is $1.5 \times 10^8 \mathrm{~ms}^{-1}$. If relative permittivity of that medium is 2 , then its magnetic susceptibility is (speed of light in vacuum is $3 \times 10^8 \mathrm{~ms}^{-1}$ ).

Match the electromagnetic radiations given in List-I with their uses given in List-II

Electromagnetic radiation of intensity $0.6 \mathrm{Wm}^{-2}$ is falling on a black surface. The radiation pressure on the surface is

A parallel-plate capacitor with circular plates is being discharged. The radius of the circular plate is 10 cm . A circular loop of radius 20 cm is concentric with the capacitor and located halfway between the plates. If the electric field between the plates is charging at the rate $3.6 \times 10^{12} \mathrm{~V} /(\mathrm{ms})$, then the displacement current through the loop is

$$\text { (Assume } \frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \mathrm{Nm}^2 / \mathrm{C}^2 \text { ) }$$

What is the amplitude of the electric field in a parallel beam of light intensity $\left(\frac{15}{\pi}\right) \frac{\mathrm{W}}{\mathrm{m}^2}$ ?

$$\left[\text { Assume }, \frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \frac{\mathrm{Nm}^2}{\mathrm{C}^2}\right]$$

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

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)

The typical wavelength of X-ray is

At an instant, a plane electromagnetic wave has its magnetic field in the direction of the vector $\hat{\mathbf{i}}-\hat{\mathbf{j}}$ and its electric field is in the direction of $\hat{\mathbf{i}}+\hat{\mathbf{j}}$. The wave is travelling along which direction?

Choose the correct statement.

The radiation energy emitted per second by a point source is 100 W . If the efficiency of the source is $4 \%$, then the rms value of the electric field at distance of 2 m is [use $\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9$ in SI unit]