Exams › JEE Main › Physics

A plane electromagnetic wave of frequency 50 MHz travels in free space along the positive x-direction. At a particular point in space and time, E = 6.3 ĵ V/m. The corresponding magnetic field B at that point will be

1. 1.85 × 10⁻⁸ k̂ T
2. 2.1 × 10⁻⁸ k̂ T
3. 18.5 × 10⁻⁸ k̂ T
4. 6.3 × 10⁻⁸ k̂ T

Correct answer: 2.1 × 10⁻⁸ k̂ T

Solution

For a plane EM wave, B0 = E0/c = 6.3/(3x10^8) = 2.1x10^-8 T. With E along +y and propagation +x, B is along +z (k-hat), so B = 2.1x10^-8 k-hat T.

Related JEE Main Physics questions

• A plane electromagnetic wave falls on a material surface. If it transfers momentum p and energy E, which statement is true?
• For an electromagnetic wave moving in vacuum, the electric field is expressed as E = E₀ sin(kx − ωt). Which of the following quantities does not depend on the wavelength?
• When an electromagnetic wave enters the ionised region of the ionosphere, the moving electron cloud gives rise to a space current, while the electric field also produces a capacitive displacement current. In this situation, what is the phase relation between the space current and the displacement current?
• The rms electric field associated with sunlight is 720 N/C. What is the mean total energy density of this electromagnetic wave?
• The electric field component of an electromagnetic wave in a medium is given by Eₓ = 0, E_y = 2.5 N/C cos[(2π × 10⁶ rad/m)x - (π × 10⁻² rad/s)t] ŷ, and E_z = 0. The wave is:
• A source of monochromatic green light radiates equally in every direction. If it converts only 3% of the 100 W electrical power it uses into electromagnetic radiation, then the electric-field amplitude of the emitted wave at a point 5 m away from the source is closest to:

⚔️ Practice JEE Main Physics free + battle 1v1 →