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Question : 4
Total: 36
The absolute refractive indices of glass and water are 4 ∕ 3 and 3 ∕ 2 respectively. If the speed of light in glass is 2 × 10 8 m ∕ s , calculate the speed of light in (i) vacuum, (ii) water.
Solution:
(i) Given: n g =
, n w =
, v g = 2 × 10 8 m ∕ s
We know that for glass,
n g =
∴ Speed of light in air or vacuum,
c = n g v g
=
× 2 × 10 8 = 2.67 × 10 8 m ∕ s
(ii) Also in water,
n w =
∴ v w =
=
Speed of light in water= 1.78 × 10 8 m ∕ s .
We know that for glass,
(ii) Also in water,
Speed of light in water
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