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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 a ray of light travels from air to glass slab and strikes the surface of separation at 90°, then it …………….
(a) bends towards normal
(b) bends away from normal
(c) passes unbent
(d) passes in zigzag way
After tracing the path of a ray of light passing through a rectangular glass slab for four different values of the angle of incidence, a student reported his observations in tabular form as given below:
| S.No | ∠ i | ∠ r | ∠ e |
| I | 30° | 19° | 29° |
| II | 40° | 28° | 40° |
| III | 50° | 36° | 50° |
| IV | 60° | 40° | 59° |
The best observation is
(A) I
(B) II
(C) III
(D) IV
Draw a ray diagram to show the refraction of a monochromatic ray through a prism when it suffers minimum deviation
State the dependence of angle of deviation On the refractive index of the material of the prism.
Light passes through a rectangular glass slab and through a triangular glass prism. In what way does the direction of the two emergent beams differ and why?
Draw the diagram of refraction of light in the glass slab
Which of the above wavelengths has a higher frequency?
How is the reflection of light ray from a plane mirror different from the refraction of light ray as it enters a block of glass?
A ray of light of wavelength 6600 Å suffer refraction from air to glass. Taking \[\ce{_a\mu_g = \frac{3}{2}}\], find the wavelength of light in glass.
How does the angle of deviation produced by a prism change with increase in the angle of incidence. Draw a curve showing the variation in the angle of deviation with the angle of incidence at a prism surface.
How does the angle of minimum deviation produces by a prism change with increase in :
the refracting angle of prism?
In fig 4.18, name the ray which represents the correct path of light while emerging out through a glass block.
An object is viewed through a glass prism with its vertex pointing upwards. It appears to be displaced upward. Explain the reason.
Fig 4.31 below shows a light ray of single colour incident normally on two prisms A and B. In each case draw the path of the ray of light as it enters and emerges out of the prism. Mark the angle wherever necessary.
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.
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 total reflecting right angled isosceles prism can be used to deviate a ray of light through:
(a) 30° (b) 60° (c) 75° (d) 90°.
A student has traced the path of a ray of light through a glass slab as follows. If you are asked to label 1, 2, 3 and 4, the correct sequencing of labeling ∠i, ∠e, ∠r and lateral displacement respectively is
(a) 2, 1, 3, 4
(b) 1, 2, 3, 4
(c) 1, 3, 2, 4
(d) 1, 3, 4, 2
While performing the experiment on tracing the path of a ray of light through a rectangular glass slab, in which of the following experimental set-ups is a student likely to get best results? P1 and P2 are the positions of pins fixed by him.
(A) I
(B) II
(C) III
(D) IV
Rahim recorded the following sets of observations while tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence.
|
S. No. |
Angle of incidence |
Angle of refraction |
Angle of emergence |
|
I |
45° |
41° |
45° |
|
II |
40° |
38° |
38° |
|
III |
45° |
41° |
40° |
|
IV |
41° |
45° |
41° |
The correct observation is recorded at serial number:
(1) I
(2) II
(3) III
(4) IV
A ray of light passes from air to water. In fig. 39, which of the ray A, B, C and D is the correct refracted ray?
In the fig. name the ray which represents the correct path of light while passing through a glass block.
Light of a single colour is passed through a liquid having a piece of glass suspended in it. On changing the temperature of liquid, at a particular temperature, the glass piece is not seen.
Why is the light of a single colour used ?
Choose the correct alternative and rewrite the following:
A glass slab is placed in the path of convergent light. The point of convergence of light
Name one main factor on which the direction of bending of a ray of light depends.
In what condition a prism is said to be in the position of minimum deviation? What is the direction of the refracted ray inside the prism in this condition?
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?
The figure shows two prisms A and B. A monochromatic ray of light PO is incident at the face of the prism A. Complete the diagram to show the path of the ray till it emerges out of the prism B.
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.
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.
What should be the rate of the speed of light through the liquid to the speed through the glass so that there is no refraction of light at the boundaries of the glass block when the system is illuminated by the light of one colour?
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.
A ray of light PQ is incident normally on the hypotenuse of a right-angled prism ABC as shown in the diagram given below:
(i) Copy the diagram and complete the path of the ray PQ till it emerges from the prism.
(ii) What is the value of the angle of deviation of the ray?
(iii) Name an instrument where this action of the prism is used.
The refractive index of glass with respect to air is 1.5. What is the value of the refractive index of air with respect to glass?
A ray of light is incident at an angle of 45° on one face of a rectangular glass slab of thickness 10 cm and refractive index 3/2. Calculate the lateral shift produced ______.
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?
