When a light ray enters a rectangular glass slab, it bends towards the normal when entering the denser medium (glass) and away from the normal when leaving it. The emergent ray is parallel to the incident ray but displaced sideways.
In the given figure, \( PQ \) and \( PR \) are tangents to the circle such that \( PQ = 7 \, \text{cm} \) and \( \angle RPQ = 60^\circ \).
The length of chord QR is: