Refractive Index Numericals class 10 & practice problems

In this post, we will solve a bunch of Numerical problems on the refractive index of light (class 10 Light chapter in Physics). The refractive index is written as RI as well. Students may try and solve these refractive index practice problems, to understand the inherent concepts of RI. The formulas used to solve the refractive index numerical problems are also given separately on this page.

Refractive index Numericals class 10 | Numerical problems on the refractive index

Q1 ] The speed of light in air is 3 x 10^8 m/s and in glass, it is 2×10^8 m/s. The RI of glass is ________________.

Solution:
RI of glass = speed of light in air /speed of light in glass = (3 x 10^8)/(2 x 10^8) = 1.5

Q2 ] The speed of light in water is 2.25 x 10^8 m/s. So the RI of water is:

Solution:
air µwater = C / V
= speed of light in air/speed of light in water
= ( 3 x 10^8) / (2.25 x 10^8) =1.33

Q3 ] The RI of the diamond is 2.41. What is the speed of light in a diamond?

Solution:
RI of diamond = speed of light in air /speed of light in the diamond
=> µdiamond =C / Vdiamond
=> Vdiamond = C / µdiamond

= (3 x 10^8) / 2.41 m/s = 1.24 x 10^8 m/s

4 ] Refractive index(RI) of glass is 1.5 and that of water is 1.33.
What is the RI of glass with respect to water?
What is the RI of water with respect to glass?

Solution:
The Refractive index(RI) of glass (µglass)is 1.5
and Refractive index(RI) of water(µwater) is 1.33
Now, RI of glass with respect to water
= waterµglass = µglass / µwater = 1.5 /1.33 = 1.127

RI of water with respect to glass = glassµwater = µwater / µglass = 1.33/1.5 = 0.89

Refractive index questions & numericals – Formulas to use

Here, is a list of formulas that will help to solve the refractive index numericals for class 10.

  1. (Absolute Refractive Index – also called Refractive index or RI of a medium)
    µ = speed of light in vacuum (or air) / speed of light in that medium = c/V
  2. 1µ2 = RI of the second medium with respect to the first medium
    = (speed of light in medium 1) / (speed of light in medium 2)
  3. 1µ2 = RI of the second medium with respect to the first medium
    = (Absolute RI of the second medium) / (Absolute RI of the first medium)
  4. 2μ1 = 1μ2
    This means, the RI of the first medium with respect to the second medium = 1 / [RI of the second medium with respect to the first medium]

Refractive Index practice problems

1] The Refractive index of glass is 1.5. If the speed of light in the air (or vacuum) is 3 X 108 m/s, find the velocity of light in the medium.

2] The RI of glass with respect to water is 1.127. Find out the RI of water with respect to glass.

3] The speed of light in a diamond is 1.24 x 10^8 m/s. What is the RI of the diamond?

Refractive Index Numericals class 10 & practice problems
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