Q1
What is a lens?
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Q2
Name the two kinds of lens? Draw diagrams to illustrate them.
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Q3
State difference between a convex and a concave lens in their —
(a) appearance, and
(b) action on the incident light.
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Q4
Which lens is converging —
(i) an equiconcave lens or an equiconvex lens?
(ii) a concavo-convex lens or a convexo-concave lens?
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(i) an equiconcave lens or an equiconvex lens?
(ii) a concavo-convex lens or a convexo-concave lens?
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Q5
Out of the two lenses, one concave and the other convex, state which one will show the divergent action on a light beam. Draw diagrams to illustrate your answer.
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Q6
Show by a diagram the refraction of two light rays incident parallel to the principal axis on a convex lens by treating it as a combination of a glass slab and two triangular glass prisms.
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Q7
Show by a diagram the refraction of two light rays incident parallel to the principal axis on a concave lens by treating it as a combination of a glass slab and two triangular glass prisms
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Q8
How does the action of the convex lens differ from that of a concave lens on a parallel beam of light incident on them? Draw diagrams to illustrate your answer.
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Q9
Define the term principal axis of a lens.
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Q10
Explain the optical centre of a lens with the help of proper diagram(s).
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Q11
A ray of light incident at a point on the principal axis of a convex lens passes undeviated through the lens.
(a) What special name is given to this point on the principal axis?
(b) Draw a labelled diagram to support the answer in part (a).
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(a) What special name is given to this point on the principal axis?
(b) Draw a labelled diagram to support the answer in part (a).
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Q12
State the condition when a lens is called equiconvex or equi-concave.
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Q13
Define the term principal foci of a convex lens and illustrate your answer with the aid of proper diagrams.
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Q14
Define the term principal foci of a concave lens and show them with the help of proper diagrams.
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Q15
Draw a diagram to represent the second focus of a concave lens.
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Q16
Draw a diagram to represent the second focus of a convex lens.
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Q17
A ray of light, after refraction through a concave lens emerges parallel to the principal axis.
(a) Draw a ray diagram to show the incident ray and its corresponding emergent ray.
(b) The incident ray when produced meets the principal axis at a point F. Name the point F
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(a) Draw a ray diagram to show the incident ray and its corresponding emergent ray.
(b) The incident ray when produced meets the principal axis at a point F. Name the point F
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Q18
A ray of light, after refraction through a convex lens emerges parallel to the principal axis.
(a) Draw a ray diagram to show it.
(b) The incident ray passes through a point F on the principal axis. Name the point F.
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(a) Draw a ray diagram to show it.
(b) The incident ray passes through a point F on the principal axis. Name the point F.
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Q19
A beam of light incident on a convex lens parallel to its principal axis converges at a point F on the principal axis. Name the point F. Draw a ray diagram to show it.
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Q20
A beam of light incident on a thin concave lens parallel to its principal axis diverges and appears to come from a point F on the principal axis. Name the point F. Draw a ray diagram to show it.
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Q21
Define the term focal length of a lens.
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Q22
What do you mean by focal plane of a lens?
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Q23
State the condition for each of the following :
(a) a lens has both its focal lengths equal.
(b) a ray passes undeviated through the lens.
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(a) a lens has both its focal lengths equal.
(b) a ray passes undeviated through the lens.
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Q24
A parallel oblique beam of light falls on a
(i) convex lens,
(ii) concave lens.
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(i) convex lens,
(ii) concave lens.
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Q25
The diagram below shows a lens as a combination of a glass slab and two prisms.
(i) Name the lens formed by the combination.
(ii) What is the line XX' called?
(iii) Complete the ray diagram and show the path of the incident ray AB after passing through the lens.
(iv) The final emergent ray will either meet XX' at a point or appear to come from a point on XX'. Label the point as F. What is this point called?
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(i) Name the lens formed by the combination.
(ii) What is the line XX' called?
(iii) Complete the ray diagram and show the path of the incident ray AB after passing through the lens.
(iv) The final emergent ray will either meet XX' at a point or appear to come from a point on XX'. Label the point as F. What is this point called?
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Q26
The diagram below shows a lens as a combination of a glass slab 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 AB 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?
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(i) Name the lens formed by the combination.
(ii) What is the line XX' called?
(iii) Complete the path of the incident ray AB 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?
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Q27
In figure (a) and (b), F1 and F2 are the positions of the two foci of thin lenses. Draw the path taken by the light ray AB after it emerges from each lens.
(a) Figure a
(b) Figure b
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(a) Figure a
(b) Figure b
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Q28
In figure (a) and (b), F1 and F2 are the two foci of thin lenses and AB is the incident ray. Complete the diagram to show the path of the ray AB after refraction through the lens.
(a) Figure a
(b) Figure b
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(a) Figure a
(b) Figure b
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Q29
Complete the following sentences —
(a) If half part of a convex lens is covered, the focal length __________ change, but the intensity of image _________.
(b) A convex lens is placed in water. Its focal length will ________.
(c) The focal length of a thin convex lens is _________ than that of a thick convex lens.
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(a) If half part of a convex lens is covered, the focal length __________ change, but the intensity of image _________.
(b) A convex lens is placed in water. Its focal length will ________.
(c) The focal length of a thin convex lens is _________ than that of a thick convex lens.
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Multiple Choice type Questions :
Q1
A ray of light after refraction through a lens emerges parallel to the principal axis of the lens. The incident ray either passes through :
1. its optical centre
2. its first focus
3. its second focus
4. the centre of curvature of the first surface
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1. its optical centre
2. its first focus
3. its second focus
4. the centre of curvature of the first surface
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Q2
A ray of light incident on a lens parallel to its principal axis, after refraction passes through or appears to come from:
1. its first focus
2. its optical centre
3. its second focus
4. the centre of curvature of its second surface.
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1. its first focus
2. its optical centre
3. its second focus
4. the centre of curvature of its second surface.
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