A uniform plane wave in air impinge at $$45^\circ$$ angle on a lossless dielectric material with dielectric constant $$\epsilon_r$$. The transmitted wave propagates in a $$30^\circ$$ direction with respect to the normal. The valueof $$\epsilon_r$$ is

A

1.5

B

$$\sqrt{1.5}$$

C

2

D

$$\sqrt 2$$