NEETPhysicsElectromagnetic Waves
The electric field of a plane electromagnetic wave in vacuum is given by E = 60 (1.5 10^7 t - 0.05 z ) i V/m . The corresponding magnetic field vector equation will be:
Options
- A2 10⁻⁷ (1.5 10^7 t - 0.05 z ) (- j ) T
- B2 10⁻⁷ (1.5 10^7 t - 0.05 z ) j T
- C1.8 10¹⁰ (1.5 10^7 t - 0.05 z ) j T
- D1.8 10¹⁰ (1.5 10^7 t - 0.05 z ) (- j ) T
Correct answer
B. 2 10⁻⁷ (1.5 10^7 t - 0.05 z ) j T
Step-by-step solution
Given, E = 60 (1.5 10^7 t - 0.05 z ) i V/m Comparing with the standard equation E = E₀ ( t - k z) i , we get: E₀ = 60 V/m = 1.5 10^7 rad/s k = 0.05 rad/m The speed of the wave is c = k = 1.5 10^7 0.05 = 3 10^8 m/s . The amplitude of the magnetic field is B₀ = E₀ c = 60 3 10^8 = 2 10⁻⁷ T . The argument ( t - k z) indicates that the wave is propagating in the +z direction, so the unit vector of propagation is k . The direction of propagation is given by E B . i B = k Since i j = k , the magnetic field must oscillate