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An electromagnetic wave of intensity 50 W m\(^{-2}\) enters a medium of refractive index \(n\) without any loss. The ratio of the magnitudes of the electric fields before and after entering the medium, and the ratio of the magnitudes of the magnetic fields before and after entering the medium, are respectively given by:

1. \(n,\,n\)
2. \(\dfrac{1}{n},\,n\)
3. \(n,\,\dfrac{1}{n}\)
4. \(\dfrac{1}{n},\,\dfrac{1}{n}\)

Correct answer: \(\dfrac{1}{n},\,n\)

Solution

For an electromagnetic wave entering a medium of refractive index \(n\), the speed becomes \(c/n\). Since \(E/B=v\), the electric field scales as \(1/n\) and the magnetic field scales as \(n\) when comparing before and after entering the medium.

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