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प्रश्न
Define refraction and state the laws of refraction.
उत्तर
The phenomenon of change in the direction of propagation of light when it passes obliquely from one transparent medium to another is called refraction of light.
Laws of refraction:-
- The incident ray and the refracted ray are on the opposite sides of the normal at the point of incidence, and all three lie in the same plane.
- For a given pair of media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant.
`sin i/sin r=mu`
This constant is called the refractive index of the second medium with respect to the first medium.
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संबंधित प्रश्न
Draw a ray diagram to show the refraction of light through a glass slab and mark angle of refraction and the lateral shift suffered by the ray of light while passing through the slab.
If the speed of light in vacuum is 3 × 108 ms−1, find the speed of light in a medium of absolute refractive index 1.5.
A student very cautiously traces the path of a ray through a glass slab for different values of the angle of incidence (∠i). He then measures the corresponding values of the angle of refraction (∠r) and the angle of emergence (∠e) for every value of the angle of incidence. On analysing these measurements of angles, his conclusion would be
(A) ∠i > ∠r > ∠e
(B) ∠i = ∠e > ∠r
(C) ∠i < ∠r < ∠e
(D) ∠i = ∠e < ∠r
Which colour of light travels fastest in any medium except air?
For which colour of white light, is the refractive index of a transparent medium the most?
In the adjacent diagram, AO is a ray of light incident on a rectangular glass slab.
- Complete the path of the ray till it emerges out of the slab.
- In the diagram, mark the angle of incidence (i) and the angle of refraction (r) at the first interface. How is the refractive index of glass related to the angles i and r?
- Mark angles of emergence by the letter e. How are the angles i and e related?
- Which two rays are parallel to each other? Name them.
- Indicate in the diagram the lateral displacement between the emergent ray and the incident ray. State one factor that affects the lateral displacement.
Fill in the blanks to complete the following sentence
The refractive index of glass with respect to air is 3/2. The refractive index of air with respect to glass will be ……………….
A Water pond appears to be 2.7 m deep. If the refractive index of water is 4/3, find the actual depth of the pond.
What is meant by the statement the critical angle for diamond is 24°?
A ray of light OP passes through a right angles prism as shown in the adjacent diagram.
(a) State the angles of incidence at the faces AC and BC.
(b) Name the phenomenon which the ray suffers at the face AC.
A student traces the path of a ray of white light through a rectangular glass slab and marks, the angles of incidence (∠i) , refraction (∠r) and emergence (∠e) as shown. Which angle or angles has he not marked correctly?
(A) ∠i only
(B) ∠i and ∠r
(C) ∠i and ∠e
(D) ∠r and ∠e
Four students showed the following traces of the path of a ray of light passing through a rectangular glass slab.
The trace most likely to be correct is that of student
(A) I
(B) II
(C) III
(D) IV
Define the term refractive index of a medium. What do you understand by the statement 'the refractive index of glass is 1.5 for white light'?
In the fig. name the ray which represents the correct path of light while passing through a glass block.
Fig shows a lens as a combination of a glass block and two prisms.
(i) Name the lens formed by the combination.
(ii) What is the line XX' called?
(iii) Complete the path of the incident ray PQ after passing through the lens.
(iv) The final emergent ray either meets XX' at a point or appears to come from a point on XX'. Label it as F, What is this point called?
Draw a diagram to show the splitting of white light into its constituent colours.
The critical angle for glass-air interface is :
A total reflecting equilateral prism can be used to deviate a ray of light through:
A ray of light passes from water to air. How does the speed of light change?
Which colour of light travels fastest in any medium except air?
During sunset and sunrise, the sun is seen when it is slightly below the horizon. Give reason.
State the relation between the refractive index μ and the velocity of light (vm) in that medium.
Define the term refractive index of a medium in terms of velocity of light.
Can the absolute refractive index of a medium be less than one?
What is the total reflecting prism?
How does the angle of deviation produced by a prism depend on the colour of light used? Which colour of white light is deviated (i) most, (ii) least, by a prism?
A ray of monochromatic light is incident from air into a glass slab. Draw a labelled ray diagram indicating the change in its path till it emerges out of the slab. In the diagram, mark the angle of incidence (i) and the angle of refraction (r) at the first interface. How is the refractive index of glass related to the angles i and r?
How does the angle of deviation produced by a prism depend on the angle of incidence of light at the prism surface? Draw a graph to illustrate your answer.
The diagram shows the path of a ray of light through a rectangular glass block placed in a liquid of uniform density.
Show with the help of a ray diagram the path of the ray when incident ray normally falls on the first surface of the glass block and passes through the block and the liquid.
Trace a ray of light incident at 30° on a surface if travelling from air to glass. What is the angle of refraction in this case? (R.I. for glass = 3/2).
Explain with the help of a diagram of how fish is able to see the objects above it.
Calculate the velocity of light in a glass block of refractive index 1.5. (Velocity of light in air = 3 × 108 m/s)
A glass block is having refractive index 3/2, the light ray is incident at an angle 45°. Find the sine of the angle of, refraction inside the glass block.
Draw the ray diagram of a glass slab having medium A and B for the velocity of light ray VA and VB respectively and define Snell's law.
- If VB = 1.5 VA, then which medium is denser?
- What is the refractive index of A with respect to B?
- What is the refractive index of B with respect to A?
