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प्रश्न
What is the correct reason for blinking / flickering of stars? Explain it.
a) The blasts in the stars.
b) Absorption of star light by the atmosphere.
c) Motion of the stars.
d) Changing refractive index of gases in the atmosphere.
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उत्तर
d) Changing refractive index of gases in the atmosphere.
Atmosphere is unstable due to changing density and temperature of air, hence refractive index of air keeps changing continuously. The position and brightness of the star keep changing continuously and the star appears to be twinkling.
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संबंधित प्रश्न
When rays of light are incident on a glass slab then the incident ray and emergent ray are _________ each other.
- perpendicular
- parallel
- opposite
- concurrent
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.
Why is the ratio of the velocities of light of wavelengths 4000Å and 8000Å in vacuum 1: 1?
Write the relation between the angle of incidence and the angle of refraction for a medium.
How is the angle of emergence related to the angle of incidence when prism is in the position of minimum deviation? Illustrate your answer with help of a labelled diagram using an equilateral prism?
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.
Select from the following the best experimental set-up for tracing the path of a ray of light through a glass slab:
(A) I
(B) II
(C) III
(D) IV
“A ray of light incident on a rectangular glass slab immersed in any medium emerges parallel to itself.” Draw labelled ray diagram to justify the statement.
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 A, B, C and D traced the paths of incident ray and the emergent ray by fixing pins P and Q for incident ray and pins R and S for emergent ray for a ray of light passing through a glass slab.
The correct emergent ray was traced by the student:
(1) A
(2) B
(3) C
(4) D
Observe the figure and write accurate conclusion regarding refraction of light.
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'?
How does the deviation produced by a prism depend on the refraction index of its material.
The critical angle for glass-air interface is :
Name the phenomenon responsible in the following case:
Twinkling of stars
Why does a fisherman aim at the tail of fish during spearfishing?
Why upper surface of water contained in a beaker and above eye level appears silvery?
Write a relation between the angle of incidence (i), angle of emergence (e), angle of the prism (A), and angle of deviation (d) for a ray of light passing through an equilateral prism.
State the factors on which the angle of deviation depends.
What is the refractive index of vacuum
What is the refractive index of water
Comment on the statement ‘The refractive index of glass is 3/2.’
Express the refractive index μ of a medium in terms of the velocity of light.
In the diagram below, PQ is a ray of light incident on a rectangular glass block.
Copy the diagram and complete the path of the ray of light through the glass block. In your diagram, mark the angle of incidence by letter ‘i’ and the angle of emergence by the letter ‘e’.
In the diagram alongside a ray of light, PQ is incident normally on one face AB of an equilateral glass prism. What is the angle of incidence at the faces AB and AC?
Two parallel rays of Red and Violet travelling through the air, meet the air-glass boundary as shown in the above figure. Will their paths inside the glass be parallel? Give a reason for your answer.
A ray of monochromatic light is incident from the air on a glass slab:
(i) Draw a labelled ray diagram showing the change in the path of the ray till it emerges from the glass slab.
(ii) Name the two rays that are parallel to each other.
(iii) Mark the lateral displacement in your diagram.
The diagram shows the path of a ray of light through a rectangular glass block placed in a liquid of uniform density.
(a) Does the light speed up or slow down in the glass,
(b) Give the reason for your answer.
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).
Trace a ray of light incident at 30° on a surface if travelling from glass to air. What is the angle of refraction in this case? (R.I. for glass = 3/2).
Draw a diagram of a prism and label:
(i) the base,
(ii) the refracting surfaces,
(iii) the refracting edge,
(iv) the refracting angle in it.
The speed of light in air is 3 × 108 ms-1. Calculate the speed of light in water. The refractive index of water is 4/3.
Observe the figure and name the ray AB, ray CD, ray GH.
A ray of light strikes the surface of a rectangular glass slab such that the angle of incidence in air is
- 0°,
- 45°.
In each case, draw a diagram to show the path taken by the ray as it passes through the glass slab and emerges from it.
