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If in a medium, the speed of light is 1.5 × 108 m/s how much will the absolute refractive index of that medium be? - Science and Technology 1

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प्रश्न

If in a medium, the speed of light is 1.5 × 108 m/s how much will the absolute refractive index of that medium be?

Solve the example.
If the speed of light in a medium is 1.5 × 108 m/s, what is the absolute refractive index of the medium?

संख्यात्मक

उत्तर १

Absolute refractive index of a medium μ = `"Speed of light in vaccum"/ "Speed of light in the medium"`
⇒ μ = `(3 xx 10^8)/(1.5 xx 10^8) = 2`

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उत्तर २

Given: Speed of light in medium (v2) = 1.5 × 108 m/s,
velocity of light in vacuum (v1) = 3 × 108 m/s

To find: Absolute refractive index (n)

Formula: n = `"v"_1/"v"_2`

Calculation: From the formula,

n = `(3 xx 10^8)/(1.5 xx 10^8)` = 2

The absolute refractive index of the medium is 2.

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अध्याय 6: Refraction of light - Solve the following Questions

संबंधित प्रश्न

How refraction of light is related to refractive index?


The absolute refractive indices of two media 'A' and 'B' are 2.0 and 1.5 respectively. If the speed of light in medium 'B' is 2 × 108 m/s, calculate the speed of light in:

(i) vacuum,

(ii) medium 'A'.


A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?


The refractive index of diamond is 2.42. What is the meaning of this statement?


A ray of light travelling in air goes into water. The angle of refraction will be:

(a) 90°
(b) smaller than the angle of incidence
(c) equal to the angle of incidence
(d) greater than the angle of incidence


The speed of light in air is:

(a) 3 × 108 cm/s
(b) 3 × 108 mm/s
(c) 3 × 108 km/s
(d) 3 × 108 m/s


Which of the following diagrams shows the ray of light refracted correctly?


What is the unit of refractive index? 


Refractive indices of carbon disulphide and ethyl alcohol are 1.63 and 1.36 respectively. Which is optically denser?


Give three examples of materials that refract light rays. What happens to the speed of light rays when they enter these materials?


The speed of light in air is 3 × 108 m/s. In medium X its speed is 2 × 108 m/s and in medium Y the speed of light is 2.5 × 108 m/s Calculate:

(aair nx
(bair nY
(cx n


 State and explain the laws of refraction of light with the help of a labelled diagram. 


The refractive indices of four substance P, Q, R and S are 1.50, 1.36, 1.77 and 1.31 respectively. The speed of light is the maximum in the substance: 

(aP
(bQ
(cR
(d


The refractive index of glass for light going from air to glass is .

The refractive index for light going from glass to air will be:

(a) `1/3`

(b) `4/5`
(c) `4/6` 
(d) `5/2`


The refractive index of water is:

(a) 1.33
(b) 1.50
(c) 2.42
(d) 1.36


Refractive indices of water, sulphuric acid, glass and carbon disulphide are 1.33, 1.43, 1.53 and 1.63 respectively. the light travels slowest in:

(a) sulphuric acid
(b) glass
(c) water
(d) carbon disulphide  


Define the term absolute refractive index. The absolute refractive index of diamond is 2.42. What is the meaning of this statement? Refractive indices of media A, B C and D are given below:

Media

Refractive index

A

1.33

B

1.44

C

1.52

D

1.65

In which of these four media is the speed of light (i) minimum and (ii) maximum ?

Find the refractive index of medium C with respect to medium B.


State the law of refraction of light that defines the refractive index of a medium with respect to the other. Express it mathematically. How is refractive index of any medium 'A' with respect to a medium 'B' related to the speed of propagation of light in two media A and B? State the name of this constant when one medium is vacuum or air.

The refractive indices of glass and water with respect to vacuum are 3/2 and 4/3 respectively. If the speed of light in glass is 2 × 108m/s, find the speed of light in (i) vacuum, (ii) water.


Fill in the blank and Explain the completed sentences.
 Refractive index depends on the ______ of light.


Mark the correct answer in the  question.

 If the refractive index of glass with respect to air is 3/2, what is the refractive index of air with respect to glass?


_______ is the unit of refractive index.


If the refractive index of air with respect to glass is 2/3. What is the refractive index of glass with respect to air?


2n1 : Refractive index of medium 2 with respect to medium 1 : : 1n2 : _______


Refractive index of air : 1.0003 : : refractive index of water : _______


Define the refractive index of a medium.


A light ray enters from medium A to medium B as shown in figure. The refractive index of medium B relative to A will be ______.


Noor, a young student, was trying to demonstrate some properties of light in her Science project work. She kept ‘X’ inside the box (as shown in the figure) and with the help of a laser pointer made light rays pass through the holes on one side of the box. She had a small butter-paper screen to see the spots of light being cast as they emerged.

If the object inside the box was made of a material with a refractive index less than 1.5 then the ______.


Refractive index of diamond with respect to glass is 1.6 and absolute refractive index of glass is 1.5. Find out the absolute refractive index of diamond.


The velocity of light in a vacuum is 3 x 108 ms-1 and in glass is 2 x 108 ms-1. The refractive index of glass is ______.


How is the refractive index of material related to the velocity of light?


What happens when a light ray passes from a rarer medium to a denser medium?


The refractive index of glass with respect to air is `5/4` and the refractive index of water with respect to air is `4/3`. Then what will be the refractive index of glass with respect to water?


Match the pair:

Group 'A'   Group 'B'
Substance   Refractive index
Air (a) 1.33
  (b) 1.46
  (c) 1.0003

A light ray enters from medium A to medium B as shown in the figure.

Which one of the two media is denser w.r.t. other medium? Justify your answer.


The ability of medium to refract light is expressed in terms of its optical density. Optical density has a definite connotation. It is not the same as mass density. On comparing two media, the one with the large refractive index is optically denser medium than the other. The other medium with a lower refractive index is optically rarer. Also the speed of light through a given medium is inversely proportional to its optical density.
  1. Determine the speed of light in diamond if the refractive index of diamond with respect to vacuum is 2.42. Speed of light in vacuum is 3 × 108 m/s. 
  2. Refractive indices of glass, water and carbon disulphide are 1.5, 1.33 and 1.62 respectively. If a ray of light is incident in these media at the same angle (say θ), then write the increasing order of the angle of refraction in these media. 
  3. (A) The speed of light in glass is 2 × 108 m/s and is water is 2.25 × 108 m/s.
    (a) Which one of the two optically denser and why?
    (b) A ray of light is incident normally at the water glass interface when it enters a thick glass container filled with water. What will happen to the path of the ray after entering the glass? Give reason. 
    OR
    (B) The absolute refractive indices of glass and water are 4/3 and 3/2, respectively. If the speed of light in glass is 2 × 108 m/s, calculate the speed of light in (i) vacuum (ii) water.

Absolute refractive indices of glass and water are `3/2 and 4/3` respectively. If the speed of light in glass is 2 × 108 m/s, the speed of light in water is ______.


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