Study Guides/Physics/Refractive Index of Air
Study Guide · Physics

What is the Refractive Index of Air and Water?

In Class 10 Physics (Light: Reflection and Refraction), you learn that light bends (refracts) when it enters a new medium because its speed changes. The amount of bending is measured by the Refractive Index.

Question (Click to Flip)

What is the refractive index of air?

Answer

The absolute refractive index of air is 1.0003. For mathematical calculations, it is generally taken as 1.

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Key Facts

Formula: n = c / v.

Refractive index of Air: 1.0003 (~ 1).

Refractive index of Water: 1.33.

Refractive index of Diamond: 2.42 (Highest).

What is Absolute Refractive Index?

The Absolute Refractive Index (n) of a medium is the ratio of the speed of light in a vacuum (c) to the speed of light in that specific medium (v).

Formula: $n = \frac{c}{v}$

Note: Because it is a ratio of two speeds, the refractive index has no unit.

The Refractive Index of Air

  • Vacuum: The refractive index of a perfect vacuum is exactly 1.0000.
  • Air: Light travels almost as fast in the air as it does in a vacuum. Therefore, the refractive index of air is 1.0003. (For almost all Class 10 numerical problems, we round this off and consider the refractive index of air as 1).

Refractive Index of Other Mediums

  • Water: 1.33 (Light travels slower in water than in air).
  • Glass (Crown): 1.52
  • Diamond: 2.42 (This is the highest refractive index of any natural material, which means light travels extremely slowly through a diamond, causing it to sparkle brilliantly).

Questions and Answers

What is the refractive index of air?+

The absolute refractive index of air is 1.0003. For mathematical calculations, it is generally taken as 1.

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