Electromagnetic Waves MCQs for NEET — Physics Questions with Answers

Electromagnetic waves with a wavelength of the order of a few metres were first produced and detected in the laboratory by Hertz in 1887. He thus verified a basic prediction of Maxwell's equations. (Context: 'Electromagnetic waves with wavelength of the order of a few metres were first produced and detected in the laboratory by Hertz in 1887.')

Electromagnetic waves are self-sustaining oscillations of electric and magnetic fields. They do not require a material medium and propagate even in vacuum, making them transverse waves. The electric and magnetic fields oscillate sinusoidally in space and time, are perpendicular to each other, and to the direction of propagation. (Context: 'They are self-sustaining oscillations of electric and magnetic fields in free space, or vacuum. They differ from all the other waves we have studied so far, in respect that no material medium is involved... The oscillating electric and magnetic fields... are perpendicular to each other, and to the direction of propagation of the electromagnetic wave.')

An oscillating charge produces an oscillating electric field, leading to an electromagnetic wave. The frequency of the electromagnetic wave naturally equals the frequency of oscillation of the charge. (Context: 'The frequency of the electromagnetic wave naturally equals the frequency of oscillation of the charge.')

$B_0 = E_0/c = 48/(3\times 10^8) = 1.6\times 10^{-7}\ \text{T}$.

EM waves are produced by accelerating charges, not uniformly moving ones.

In the gap $I_\text{disp} = \epsilon_0\,d\Phi_E/dt$ equals the conduction current $I$ and points the same way.

$B_0 = \dfrac{E_0}{c} = \dfrac{60}{3\times10^8} = 2\times10^{-7}\ \text{T}$. With $\vec E$ along $z$ and propagation along $-x$, $\vec B$ is along $y$: $B_y = 2\times10^{-7}\cos(5x+1.5\times10^9 t)$.

The displacement current produces a magnetic field that is non-zero everywhere and is maximum on the cylindrical surface joining the plate edges (at $r = R$).