CBSE Class 10 Science 2016 Term II Outside Delhi Set 3

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Question : 4
Total: 11
The refractive indices of glass and water with respect to air are 32 and 43 respectively. If speed of light in glass is 2×108m s, find the speed of light in water.
Solution:  
Refractive index of a medium
=
Speed of light in air
Speed of light in the medium

For glass,
3
2
=
Speed of light in air
2×108

Speed of light in air =
3
2
×2
×108
=3×108m s
.
For water,
4
3
=
Speed of light in air
Speed of light in water

Speed of light in water
=3×108×
3
4
=2.25×108m s
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