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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
Explain how spectrum is formed.
What is a spectrum?
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.
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Name one factor that affects the lateral displacement of light as it passes through a rectangular glass slab.
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The following diagram shows a 60°, 30°, 90° glass prism of critical angle 42°, Copy the diagram and complete the path of incident ray AB emerging out of the prism marking the angle of incidence on each surface.

A ray of light passes from glass into air. The angle of refraction will be:
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(d) 45°
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Complete Fig. 4.32 to show the path of the ray of single colour as it enters the prism and emerges out of it. Mark the angles wherever necessary.
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Select from the following the best set-up for tracing the path of a ray of light through a rectangular glass slab:

(A) I
(B) II
(C) III
(D) IV
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If a ray of light strikes a glass slab at an angle of 600 with the surface of the slab, the angle of incidence must be __________________.
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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?

A ray of monochromatic light is incident from the air on a glass slab:
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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.
The diagram shows the path of a ray of light through a rectangular glass block placed in a liquid of uniform density.

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- What is the refractive index of B with respect to A?
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