Exams › JEE Main › Physics

An EM wave propagating in x-direction has a wavelength of 8 mm. The electric field vibrating y-direction has maximum magnitude of 60 V m^-1. Choose the correct equations for electric field and magnetic field if the EM wave is propagating in vacuum.

1. E_y = 60 sin[(π/4)×10^3(x − 3×10^8 t)] j V m^-1 B_z = 2 sin[(π/4)×10^3(x − 3×10^8 t)] k T
2. E_y = 60 sin[(π/4)×10^3(x − 3×10^8 t)] j V m^-1 B_z = 2×10^-7 sin[(π/4)×10^3(x − 3×10^8 t)] k T
3. E_y = 2×10^-7 sin[(π/4)×10^3(x − 3×10^8 t)] j V m^-1 B_z = 60 sin[(π/4)×10^3(x − 3×10^8 t)] k T
4. E_y = 2×10^-7 sin[(π/4)×10^4(x − 4×10^8 t)] j V m^-1 B_z = 60 sin[(π/4)×10^4(x − 4×10^8 t)] k T

Correct answer: E_y = 60 sin[(π/4)×10^3(x − 3×10^8 t)] j V m^-1 B_z = 2×10^-7 sin[(π/4)×10^3(x − 3×10^8 t)] k T

Solution

The correct option accurately represents the electric field with the given maximum magnitude and the appropriate wave number derived from the wavelength, while the magnetic field is calculated using the relationship between the electric and magnetic fields in a vacuum, ensuring the correct amplitude.

Related JEE Main Physics questions

• A ring carrying uniform charge has radius 10 cm and spins about its own axis with a frequency of $10^4$ revolutions per second. At a point on the axis, 20 cm from the centre, the ratio of the electric-field energy density to the magnetic-field energy density is $9.1 \times 10^{10}$. Determine the value of $a$.
• A plane electromagnetic wave falls on a material surface. If it transfers momentum \(p\) and energy \(E\), which statement is true?
• The intensity of an electromagnetic wave is given by which expression?
• For an electromagnetic wave moving in vacuum, the electric field is expressed as \(E = E_0\sin(kx - \omega t)\). 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?

⚔️ Practice JEE Main Physics free + battle 1v1 →