[单选题]
A light ray in air is incident p2ylin*d rkba+r)dzd6/ ,ue8 on an air to glass interface at an angz1v95quw1go17bren s fh,kg 76 a:wrsio *7b xle of $45^{\circ}$ and is refracted at an angle of $30^{\circ}$ to the normal. What is the index of refraction of the glass?
