- The value of sini/sinr is called the refractive index of the medium and it gives you an indication of its light-bending ability.
- In SPM, when we say “refractive index”, what we mean is the absolute refractive index of a substance. The absolute refractive index of a substance is the refractive index where light ray travels from the vacuum (or air) into the substance.
Refractive Index and the Speed of light
( Note that the greater the refractive index of a medium, the lower is the speed of light. The more light is slowed, the more it is bent. )
Real and Apparent Depth
- The bending of light can give you a false impression of depth.
- Figure to the left shows two rays of light leaving a point on the bottom of a swimming pool.
- The rays are refracted as they leave the water. To the observer, the rays seem to come from a higher position, and the bottom looks closer to the surface than it really is.
- The real depth of the water and its apparent depth are marked on the diagram. These are related to the refractive index of the water by the following equation: