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प्रश्न
Define the power of a lens.
Define the term power of a lens.
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उत्तर १
Power of a lens is defined as the ability of a lens to bend the rays of light. It is given by the reciprocal of focal length in metre.
उत्तर २
The power of a lens is a measure of the deviation produced by it in the path of rays refracted through it.
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संबंधित प्रश्न
Define 1 dioptre of power of a lens.
What is the focal length of a convex lens of focal length 30 cm in contact with a concave lens of focal length 20 cm? Is the system a converging or a diverging lens? Ignore thickness of the lenses.
Name the physical quantity whose unit is dioptre.
Which type of lens has (a) a positive power, and (b) a negative power?
A converging lens has focal length of 50 mm. What is the power of the lens?
A diverging lens has focal length of 3 cm. Calculate the power.
A convex lens of power 5 D and a concave lens of power 7.5 D are placed in contact with each other. What is the :
(a) power of this combination of lenses?
(b) focal length of this combination of lenses?
A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are placed in close contact with one another.
(a) What is the power of this combination?
(b) What is the focal length of this combination?
(c) Is this combination converging or diverging?
Two lenses A and B have focal lengths of +20 cm and, −10 cm, respectively.
(a) What is the nature of lens A and lens B?
(b) What is the power of lens A and lens B?
(c) What is the power of combination if lenses A and B are held close together?
How is the power of a lens related to its focal length?
A normal eye is not able to see objects closer than 25 cm because
A double convex lens has two surfaces of equal radii R and refractive index \[m = 1 \cdot 5\]
A diverging lens of focal length 20 cm and a converging lens of focal length 30 cm are placed 15 cm apart with their principal axes coinciding. Where should an object be placed on the principal axis so that its image is formed at infinity?
How is accommodation produced?
The power of a lens is +2.0 D. Find its focal length and state the kind of lens.
Complete the diagram to show the formation of the image of the object AB.
(i) Name the Lens LL’.
(ii) Where is the image of the object AB formed?
(iii) State three characteristics of the image.
If focal length of a convex lens is 20 cm at what is the power of the lens?
The above lens has a focal length of 10 cm. The object of height 2 mm is placed at a distance of 5 cm from the pole. Find the height of the image.
