1. | \(BC.\) | normally from the surface
2. | \(AC.\) | normally from the surface
3. | \(BC\) or \(AC,\) normally. | either from the surface
4. | \(BC\) or \(AC,\) at an angle of emergence greater than \(60^{\circ}\) but less than \(90^{\circ}.\) | either from the surface
1. | \(\dfrac32\) | 2. | \(2\) |
3. | \(\sqrt{\dfrac32} \) | 4. | \(\sqrt2\) |