A plane electromagnetic wave is travelling in an unbounded, lossless dielectric having μr = 1 and ϵr = 4. The time average pointing vector of the wave is 5 W/m3 The phase velocity Vp (assuming velocity of light as 3 × 108 m/s) is
1
3 × 108 m/s
2
2.5 × 108 m/s
3
0.5 × 108 m/s
4
1.5 × 108 m/s