[单选题]
A light ray in air is incident on an air to glassecc9,tymr1l:z.4( jm/r5f u ja4wsrb interface at an anjmp v ub7u,(ho-,3r keq6t e1egle of $45^{\circ}$ and is refracted at an angle of $30^{\circ}$ to the normal. What is the index of refraction of the glass?
