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Refraction - Critical Angle , Total Internal Reflection Some Definition Related to a Lens
Speed of Light and Reflective Index - Physics Light
2648    Arnab De    13/02/2020

Speed of light

The speed of light in vacuum and air is 3 x 108 ms-1. It is the maximum speed of light. The speed of light in air or vacuum is denoted by a symbol c. In any other transparent media (water, oil, glass), the speed of light is slower than c. The reflective index of a medium can define with respect to vacuum or air is known as absolute reflective index.  It is denoted by μ or n.

Speed of light

As we know, v is always less than c, therefore μ is always greater than 1. The reflective index of alcohol is 1.37. That means light travels in air or vacuum 1.37 times faster than in alcohol.

Reflective index of some common substance

Substance

μ or n

Substance

μ or n

Vacuum or air

1.00

Ice

1.03

Water

1.33

Methylated spirit or Ether

1.36

Alcohol

1.37

Kerosene

1.41

Sulphuric Acid

1.43

Paraffin Oil

1.44

Glycerine or turpentine oil

1.47

Glass

1.5

Diamond

2.41

Ruby

1.67

Flint Glass

165

Rock salt

1.56

Crown glass

1.53

Quartz

1.54

Reflective index of a medium in respective of another

In there are two different medium is present, in which the light is travel. Then we can calculate the reflective index of a medium in respective of another. Let there are two medium m1 and m2.

Speed of light

Example -

The reflective index of glass is 3/2 and reflective index of water 4/3.

Given,          aµg = 3/2, aµw = 4/3

Therefore, wµg = (Reflective index of glass) / (Reflective index of water) = (3/2) / (4/3) = 9 / 8 = 1.125.

Refraction - Critical Angle , Total Internal Reflection Some Definition Related to a Lens
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Author Details
Arnab De
I have over 16 years of experience working as an IT professional, ranging from teaching at my own institute to being a computer faculty at different leading institute across Kolkata. I also work as a web developer and designer, having worked for renowned companies and brand. Through tutorialathome, I wish to share my years of knowledge with the readers.
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