Electromagnetic Waves MCQs for NEET — Physics Questions with Answers

The greenhouse effect is primarily caused by the absorption and emission of infrared radiation by greenhouse gases in the Earth's atmosphere. These gases include carbon dioxide, methane, and water vapor, which trap heat and keep the planet warm.

Energy density is defined as the amount of energy stored in a given system or region of space per unit volume. The dimensional formula for energy is $ML^2T^{-2}$. Since energy density is energy per unit volume, we divide by volume, which has the dimensional formula $L^3$. Therefore, the dimensional formula of energy density is $\frac{ML^2T^{-2}}{L^3} = ML^{-1}T^{-2}$.

An optical microscope uses light in the visible range of the electromagnetic spectrum to produce magnified images of small objects. Visible light has wavelengths in the range of approximately 400 nm to 700 nm.

Total power = $Flux\times area$

$$\begin{gathered} ={10}^3\times 8\times 20 \\ =1.6\times {10}^5 W \end{gathered}$$

Displacement current is defined in terms of the rate of change of the electric field. So to have continuous displacement current, the electric field should remain changing.

An electromagnetic wave can be created by accelerating charges; moving charges back and forth will produce oscillating electric and magnetic fields, and these travel at the speed of light.

J.C. Maxwell showed that for logical consistency, a changing electric field must also produce a magnetic field. Further, since magnetic fields have always been associated with currents, Maxwell postulated that this current was proportional to the rate of change of the electric field and called it displacement current.

$\overrightarrow{S}=\overrightarrow{E}\times \overrightarrow{B}$

The electric and magnetic field components of a linearly polarized electromagnetic wave oscillate in such a way that they peak at the same time and they become zero at the same time but they point to different directions in space, separated by an angle of $900$

(b) Given root mean square value of electric field,

                $E_{rms}= 6 V/m$

We know that, peak value of electric field, 

   $E_o=\sqrt{2}{E}_{rms}$

$\Rightarrow E_o=\sqrt{2}\times 6 V/m$

Also, we know that, $c=\frac{E_o}{B_o}$

where, c= speed of light in vacuum 

$B_o= peak value of magnetic field$

$$\begin{gathered} \Rightarrow B_o=\frac{\sqrt{2}\times 6}{3\times {10}^8} \\ \Rightarrow B_o=\frac{8.48}{3}\times {10}^{-8} \\ \Rightarrow B_o=2.83\times {10}^{-8} T \end{gathered}$$