JEE Main 2014 · 6 Apr · Shift 1 · Physics Q22

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During the propagation of electromagnetic waves in a medium :

Electric energy density is double of the magnetic energy density.

Electric energy density is half of the magnetic energy density.

Electric energy density is equal to the magnetic energy density.

Both electric and magnetic energy densities are zero.

Answer and worked solution

Official answer: C

In an electromagnetic wave $B=E/v$ , so
$u_E=\tfrac12\epsilon E^2=\tfrac12\frac{B^2}{\mu}=u_B.$
The electric and magnetic energy densities are equal.

Topics:Energy and momentum of EM waves

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JEE Main 2014 · 6 Apr · Shift 1, Physics question 22