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प्रश्न
What type of lenses are used in spectacles worn by an old lady for knitting?
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उत्तर
A converging lens of suitable focal length is used in the spectacles worn by an old lady for knitting.
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संबंधित प्रश्न
State the condition when a lens is called an equi-convex or equi-concave.
The diagram below shows a lens as a combination of a glass slab and two prisms.
- Name the lens formed by the combination.
- What is the line XX’ called?
- Complete the path of the incident ray AB after passing through the lens.
- 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?

Study the diagram shown in Fig. 5.56
where is the object located?

State the condition of the following:
A lens has both its focal lengths equal.
In the following diagram , the object and the image formed by the respective lenses are shown. Complete the ray diagram, and locate the focus. Find the focal length of the lens.

Make the rrect choices in the following items :
ln fig, , a real image of a point objert O is formed, Which of the following statements is true about each of the arrangements?

(i) The object is at the principle focus of the lens
(ii) The focal length of the lens is 17 cm
(iii) lf the mirror is moved so that it is 6 cm from the lens image will also move
Make the correct choices in the following items :
A lens used as a magnifying glass
(i) ls a diverging lens
(ii) Produces a virtual image
(iii) ls placed with the object nearer the lens than the principle focus
How will you differentiate between a convex and a concave lens by looking at a distant object.
How will you differentiate between a convex and a concave lens by looking at a printed page?
Mixture of red + blue + green is passed through a convex lens as shown in the diagram below. State whether the ray passes through a single point or through different points on the principal axis after refraction.

