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Welcome to our Physics lesson on The Index of Refraction, this is the fifth lesson of our suite of physics lessons covering the topic of Refraction of Light, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
As explained earlier, light moves at different speeds in different media. This causes diffraction. To express this phenomenon mathematically, a concept known as Index of Refraction is introduced. The index of refraction is denoted by n and it is calculated by
For example, since the light speed in air is about 300 000 km/s while in water it is 225 000 km/s, the refractive indexes in air and water are:
and
The refractive index in glycerine is 1.46 and in diamond 2.4. Calculate the speed of light in glycerine and diamond.
From the formula of refractive index and giving that the speed of light in vacuum is 300 000 km/s, we obtain
Remark! Critical angle exists only when the incident medium is denser than the refractive medium as only in this case the refracted ray moves away from the normal line and so, the refraction angle becomes 900 before the incident angle.
You have reached the end of Physics lesson 12.3.5 The Index of Refraction. There are 7 lessons in this physics tutorial covering Refraction of Light, you can access all the lessons from this tutorial below.
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