EM waves, characteristics and transverse nature
Top questions
See all →- 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
- 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
- The energy that will be ideally radiated by a 100 kW transmitter in 1 hour is : Answer: 2. 36 × 10⁷ J Energy radiated equals power times time. E=Pt=100×10³\ W×3600\ s=3.6×10⁸\ J=36×10⁷\ J Option (2) is correct. 1
- For a plane electromagnetic wave propagating in x-direction, which one of the following combination gives the correct possible directions for electric field (E) and magnetic field (B) respectively ? Answer: 2. -j+k,\ -j-k Key idea: vec E , vec B and the direction of propagation are mutually perpendicular, and vec E×vec B points along pro... 1