[单选题]
A light ray in air is incident on an air to glass interface awd x lb;8ert *3mn2acke7cz1 1.rh ct9t an angle of 6y2rr9gg+ zaushzz6 -c o g,z3yg j+y4$45^{\circ}$ and is refracted at an angle of $30^{\circ}$ to the normal. What is the index of refraction of the glass?
