[问答题]
Prove in general that for a light beam incident on a f;ag8h4bu 9ib uniform layer oaix6j 3nwl pxh(al250 f transparent material, as in (Fig. Below), the direction of the emerging beam is parallel xip0n(jwx 6la25ha3 l to the incident beam, independent of the incident angle $\theta$. Assume air on both sides of the glass.
