Electromagnetic Waves MCQs for NEET — Physics Questions with Answers

In an electromagnetic wave, the electric field ( \vec{E} ), magnetic field ( \vec{B} ), and the direction of wave propagation ( \vec{k} ) are all perpendicular to each other and follow the right-hand rule. If the magnetic field is along the +ve Z direction ( \vec{B} \uparrow \hat{z} ) and the wave is propagating along the +ve X direction ( \vec{k} \uparrow \hat{x} ), then the electric field ( \vec{E} ) must be along the +ve Y direction ( \vec{E} \uparrow \hat{y} ) to satisfy the right-hand rule.

The relationship between the amplitudes of the electric field ( E_0 ) and the magnetic field ( B_0 ) in an electromagnetic wave is given by E_0 = c B_0 , where c is the speed of light in a vacuum. This relationship comes from the fact that the magnitudes of the electric and magnetic fields are related by the speed of light: E = cB .

The velocity of light in vacuum, often denoted as 'c', is a fundamental constant and does not change with frequency, wavelength, or amplitude. It is approximately 3 x 10^8 meters per second and remains consistent regardless of these factors. Therefore, the correct answer is 'none of these'.

The SI unit of displacement current is the Ampere (A). Displacement current is a quantity appearing in Maxwell's equations and is defined in terms of the rate of change of the electric field. Since it has the same units as regular current, the unit is Ampere.

Electromagnetic waves transport energy, momentum, and information, but they do not transport charge. Charge is a property of particles, not waves. Therefore, the correct option is 'Charge'.