Electromagnetic Waves MCQs for NEET — Physics Questions with Answers

From Maxwell's equations, it is seen that the magnitude of the electric and the magnetic fields in an electromagnetic wave are related as $B_0 = (E_0/c)$, which rearranges to $E_0 = B_0c$. (Context: 'It is also seen from Maxwell’s equations that the magnitude of the electric and the magnetic fields in an electromagnetic wave are related as $B_0 = (E_0/c)$ (8.10)')

In a material medium of permittivity $\epsilon$ and magnetic permeability $\mu$, the velocity of light becomes $v = 1/\sqrt{\mu\epsilon}$. (Context: '...the velocity of light becomes, $1/v = \mu\epsilon$ (8.11)')

Maxwell's equations in vacuum include Gauss's Law for electricity, Gauss's Law for magnetism, Faraday's Law, and Ampere-Maxwell Law. Kirchhoff's Current Law is a fundamental principle in circuit analysis, but not one of Maxwell's fundamental equations for electromagnetic fields. (Context: 'MAXWELL’S EQUATIONS IN VACUUM: 1. “E.dA = Q/ε0 (Gauss’s Law for electricity) 2. “B.dA = 0 (Gauss’s Law for magnetism) 3. “E.dl = – d/dt ΦB (Faraday’s Law) 4. “B.dl == µ0i + µ0ε0 d/dt ΦE (Ampere – Maxwell Law)')

Maxwell suggested the existence of an additional current, called displacement current, due to time-varying electric field and is given by $I_d = \epsilon_0 d\Phi_E/dt$. (Context: 'This displacement current is due to time-varying electric field and is given by $\epsilon_0 d\Phi_E/dt$')

In an electromagnetic wave, the oscillating electric and magnetic fields are perpendicular to each other, and both are perpendicular to the direction of propagation. If propagation is along z-direction and electric field is along y-direction, then the magnetic field must be along the x-direction. (Context: 'The oscillating electric and magnetic fields, E and B are perpendicular to each other, and to the direction of propagation of the electromagnetic wave.')

The speed 'c' of electromagnetic wave in vacuum is related to $\mu_0$ and $\epsilon_0$ (the free space permeability and permittivity constants) as $c = 1/\sqrt{\mu_0\epsilon_0}$. (Context: 'The speed c of electromagnetic wave in vacuum is related to \mu_0 and \epsilon_0 (the free space permeability and permittivity constants) as follows: $c = 1/\sqrt{\mu_0\epsilon_0}$.')

Maxwell introduced the concept of displacement current to remove an inconsistency in Ampere's circuital law when dealing with time-varying fields, which led to the prediction of electromagnetic waves. (Context: 'He suggested the existence of an additional current, called by him, the displacement current to remove this inconsistency.')

When an oscillating charge (an accelerating charge) produces an oscillating electric field, it further produces an oscillating magnetic field, which in turn creates a source for an oscillating electric field, and so on. This self-sustaining oscillation is how electromagnetic waves propagate. (Context: 'The oscillating electric and magnetic fields thus regenerate each other, so to speak, as the wave propagates through the space.')

Using Maxwell's equations for $E_x$ and $B_y$, one finds that $\omega = ck$. This is the standard relation for waves. (Context: 'Using Eqs. [8.7(a) and (b)] for $E_x$ and $B_y$ and Maxwell’s equations, one finds that $\omega = ck$, where, $c = 1/\sqrt{\mu_0\epsilon_0}$ [8.9(a)]')

Maxwell formulated a set of equations involving electric and magnetic fields, and their sources, the charge and current densities. These equations are known as Maxwell’s equations. Together with the Lorentz force formula (Chapter 4), they mathematically express all the basic laws of electromagnetism. (Context: 'Maxwell formulated a set of equations involving electric and magnetic fields, and their sources, the charge and current densities... Together with the Lorentz force formula (Chapter 4), they mathematically express all the basic laws of electromagnetism.')