JEE Main201911 Jan 2019Morning ShiftPhysicsElectromagnetic WavesActual
An electromagnetic wave of intensity 50 Wm ⁻² enters in a medium of refractive index 'n' without any loss. The ratio of the magnitudes of electric fields, and the ratio of the magnitudes of magnetic fields of the wave before and after entering into the medium are respectively, given by :
Options
- A( 1 n , 1 n )
- B( n , n )
- C( n , 1 n )
- D( 1 n , n )
Correct answer
C. ( n , 1 n )
Step-by-step solution
The speed of electromagnetic wave in free space is given by C = 1 ₀ ₀ In medium, v = 1 k ₀ ₀ (ii) Dividing equation (i) by(ii), we get C V = k = n 1 2 ₀ E ₀² C = intensity = 1 2 ₀ kE ² v E ₀² C = kE ² v E₀² E² = k V C = n² n E₀ E = n similarly B ₀² C 2 ₀ = B ² v 2 ₀ B ₀ ~B = 1 n