Final answer:
The angle at which light is completely reflected from the surface of a gem is called the critical angle. The critical angle depends on the refractive indices of the media involved. For a diamond, the critical angle is approximately 24.4°, while for water, it is approximately 48.6°.
Step-by-step explanation:
The angle at which light is completely reflected from the surface of a gem is called the critical angle. The critical angle depends on the refractive indices of the two media involved, which is the ratio of the speed of light in vacuum to the speed of light in the medium. When the angle of incidence is greater than the critical angle, total internal reflection occurs.
For example, if the gemstone in the ring is a diamond, the critical angle for light to be completely reflected from diamond to air is approximately 24.4°. This means that any light ray inside the diamond that strikes the surface at an angle greater than 24.4° will be totally reflected, making the diamond sparkle.If the gemstone was in water, the critical angle for light to be completely polarized would depend on the refractive index of water. The critical angle is given by the formula sin(critical angle) = 1 / refractive index. So, with the refractive index of water being approximately 1.33, the critical angle for water would be approximately 48.6°.