Electromagnetic Waves
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See all →- A parallel plate capacitor made of circular plates is being charged such that the surface charge density on its plates is increasing at a constant rate with time. The magnetic field arising due to displacement current is : Answer: 3. non-zero everywhere with maximum at the imaginary cylindrical surface connecting peripheries of the plates Key idea: a changing e... 1
- The electric field in a plane electromagnetic wave is given by E_z = 60(5x + 1.5×10^9 t) V/m. Then expression for the corresponding magnetic field is (here subscripts denote the direction of the field) : Answer: 1. B_y = 2×10⁻⁷cos(5x+1.5×10⁹ t)T Key idea: in an EM wave, B₀=E₀/c , and vec E×vec B points along the direction of propagation. The... 1
- A parallel plate capacitor is charged by connecting it to a battery through a resistor. If I is the current in the circuit, then in the gap between the plates : Answer: 3. displacement current of magnitude equal to I flows in the same direction as I. Key idea: Maxwell's displacement current I_d=ε₀dΦ_... 1
- The property which is not of an electromagnetic wave travelling in free space is that : Answer: 1. they originate from charges moving with uniform speed. Key idea: Electromagnetic waves are produced by accelerated (oscillating)... 1
- In a plane electromagnetic wave travelling in free space, the electric field component oscillates sinusoidally at a frequency of 2.0×10^10 Hz and amplitude 48 V m^-1. Then the amplitude of oscillating magnetic field is : (Speed of light in free space… Answer: 4. 1.6×10⁻⁷ T In an electromagnetic wave in free space, E₀ = cB₀ . B₀=E₀/c=dfrac483×10⁸=1.6×10⁻⁷ T. The frequency is not needed. The... 1
- When light propagates through a material medium of relative permittivity ε_r and relative permeability μ_r, the velocity of light, v is given by : (c - velocity of light in vacuum) Answer: 1. v = c/√(ε_r μ_r) In a medium, v=1/√(με) with μ=μ₀μ_r and ε=ε₀ε_r . Since c=dfrac1√(μ₀ε₀) , we get v=c/√(ε_rμ_r) . Option (1) is c... 1