Page 2 - Lesson note refraction of light
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Optically rarer medium
A transparent substance (medium) in which the speed of light is more is called
optically rarer medium.
Optically denser medium
A transparent substance (medium) in which the speed of light is less is known as
optically denser medium.
Glass is an optically denser medium than air and water.
Rules for refraction of light
Case 1: When light rays travel from optically rarer medium to denser medium then
they bend towards normal. In this case angle of refraction is smaller than angle of
incidence.
When light rays travel from air into glass or from air into water, it bends towards
normal. This is because the speed of light rays decreases while travelling from air
into glass or water.
Case 2: When light rays travel from optically denser medium to rarer medium then
they bend away from the normal. In this case the angle of refraction is greater than
angle of incidence.
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