What is refractive index class 10

The refractive index belongs to chapter 10 Light: Reflection and Refraction.

Refractive index

The ratio of the sine of the angle of incidence to the sine of the angle of refraction is called the refractive index of the second medium with respect of given the first medium.

When a light ray travels from an optically rarer medium to an optically denser medium, it bends toward the normal.

For a certain value of angle of incidence, there is certain value of angle of refraction.

So refractive index is the ability of a medium to bend the light ray.

 

Characteristics of refractive index

   1.   Refractive index does not depend on the value of the angle of incidence. If we increase or decrease the angle of incidence, the value of the angle of refraction will change and the ratio of sin I to sin r will remain constant for the given pair of media.

       

  `n_21=  \frac {sin ⁡i}{sin⁡ r}` 

  

  [n=  refractive index]

   2.   Refractive index is an indication of the optical density of a transparent medium.  The refractive index is the relation between the velocity of light in two particular media.

         

  ` n_21 =  \frac{\text (speed of light in medium 1)}{\text (speed of light in medium 2)} `

    

    3.   If the refractive index of medium 1 is greater than medium 2, it indicates that medium 1 is optically denser than medium 2.

 

The refractive index of some material with respect to vacuum

Material medium	Refractive index
Air	1.0003
Ice	1.31
Water	1.33
Alcohol	1.36
Fused quartz	1.46
Kerosene	1.44
Turpentine oil	1.47
Benzene	1.50
Canada balsam	1.53
Crown glass	1.52
Rock salt	1.54
CS2	1.63
Flint glass	1.65
Ruby	1.71
Sapphire	1.77
Diamond	2.42

 

What is the absolute refractive index?

The refractive index of the given medium with respect to vacuum, is called the absolute refractive index.

  ` \text(Absolute refractive index)  =  \frac{\text (speed of light in vacuum)}{\text (speed of light in medium )} `

    

    `n= c/v`

c = velocity of light in vacuum

v = velocity of light in a medium

Optical density 

Optical density is related to the bending of light by a transparent medium or substance.

Questions of refractive index

 

   1.   How to calculate refractive index?

Ans – Refractive index is calculated by dividing the speed of light in vacuum by speed of light in the given medium.

   

   2.   What does a higher refractive index mean?

 Ans – A higher refractive index indicates that light travels slowly in the medium and the light ray.

 

   3.   What is true about the refractive index of a medium?

Ans – Refractive index is independent of any change in angle of incidence or angle of refraction.

   

   4.   What is the frequency of this light in vacuum and in a material having refractive index n1?

Ans – The frequency of light remains the same in vacuum and a material with refractive index n1.

 

    5.   The refractive index of diamond is 2.42 what is the meaning of the statement?

Ans – The refractive index of diamond is 2.42 is high so speed of light will reduce in diamond by factor 2.42.

    

    6.   Which part of human eye has the maximum refractive index?

Ans – Cornea has the maximum refractive index.

    7.   Which has higher refractive index water or glass?

Ans – Glass has a higher refractive index than that water.

   

    8.   On   what factors does the refractive index of medium depend?

Ans – The refractive index of medium depends on optical density, wave length of light, colour of light, temperature.

    9.   For which colour refractive index of glass is maximum?

Ans – Refractive index of glass is maximum for violet colour.

   10.                  What is the SI unit of refractive index?

Ans – Refractive index has no SI unit.

Related Topics

Image formation by the concave mirror when -

1. Object beyond C

2. Object at C

3. Object at infinity

4. Object between C and F

5. Object between F and P