# Which of the following statements is correct in relation to electromagnetic waves in an isotropic medium?

$\begin {array} {1 1} (a)\;\text{Energy due to electric field is equal to that due to magnetic field.}\\ (b)\;\text{Electric vector E and, magnetic vector B are in phase.} \\ (c)\;\text{For a given amplitude of E vector, the intensity increases as the first power of frequency f} \\ (d)\;\text{For cylindrical wave fronts, the amplitude of the wave varies in proportion to$ \large\frac{1}{r^2}$, where$r$is the radius of the wave front.} \end {array}$

$\begin {array} {1 1} (a)\;1,3 & \quad (b)\;2,4 \\ (c)\;1,2 & \quad (d)\;2,3 \end {array}$

Ans : (c)
1,2