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प्रश्न
The following table gives the refractive indices of a few media:
| 1 | 2 | 3 | 4 | 5 | |
| Medium | Water | Crown glass | Rock salt | Ruby | Diamond |
| Refractive index | 1.33 | 1.52 | 1.54 | 1.71 | 2.42 |
Use this table to give an example of:
(i) a medium pair so that light speeds up when it goes from one of these medium to another.
(ii) a medium pair so that light slows down when it goes from one of these medium to another.
उत्तर
(1) Light speeds up as it travels from a denser medium to a rarer one, ie., from a medium with a higher refractive index to one with a lower refractive index. An example would be the medium pair of diamond and water, where light travels from diamond to water.
(2) Using the same argument, light slows down as it travels from a medium with a lower refractive index to one with a higher refractive index. Therefore, the medium pair of crown glass and ruby can be taken as an example, where light moves from the crown glass to the ruby.
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संबंधित प्रश्न
If the refractive index of glass for light going from air to glass is 3/2, find the refractive index of air for light going from glass to air.
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?
You are given kerosene, turpentine and water. In which of these does the light travel fastest? Use the information given in Table.
| Material medium |
Refractive index | Material medium | Refractive index |
| Air | 1.0003 | Canada Balsam | 1.53 |
| Ice | 1.31 | – | – |
| Water | 1.33 | Rock salt | 1.54 |
| Alcohol | 1.36 | – | – |
| Kerosene | 1.44 | Carbon disulphide | 1.63 |
| Fused quartz |
1.46 | Dense flint glass |
1.65 |
| Turpentine oil | 1.47 | Ruby | 1.71 |
| Benzene | 1.50 | Sapphire | 1.77 |
| Crown glass |
1.52 | Diamond | 2.42 |
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 refractive index of diamond is 2.42. What is the meaning of this statement in relation to the speed of light?
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:
(a) P
(b) Q
(c) R
(d) S
State Snell’s law of refraction of light. Write an expression to relate refractive index of a medium with speed of light in vacuum.
The refractive index of a medium ‘a’ with respect to medium ‘b’ is 2/3 and the refractive index of medium ‘b’ with respect to medium ‘c’ is 4/3. Find the refractive index of medium ‘c’ with respect to medium ‘a’.
Prove the statement.
If the angle of incidence and angle of emergence of a light ray falling on a glass slab are i and e respectively, prove that, i = e.
Match the Columns:
| Column ‘A’ | Column ‘B’ |
| Refractive index of water | (a) 1.31 |
| (b) 1.36 | |
| (c) 1.33 |
- Explain why the refractive index of any material with respect to air is always greater 1.
- In the figure below a light ray travels from air into the semi-circular plastic block. Give a reason why the ray does not deviate at the semi-circular boundary of the plastic block.
- Complete the ray diagram of the above scenario when the light ray comes out of the plastic block from the top flat end.
