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प्रश्न
What do you understand by the power of a lens? Name one factor on which the power of a lens depends.
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उत्तर
The power of a lens is a measure of the degree of convergence or divergence of light rays falling on it. It is defined as the reciprocal of the focal length of a lens in metres.
i.e., Power = `1/"focal length of lens (in metre)"`
Therefore, the power of a lens depends on the focal length.
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संबंधित प्रश्न
State power of a lens S.I. unit.
Find the power of a concave lens of focal length 2m.
Find the focal length of a lens of power −2.0 D. What type of lens is this?
Ranbir claims to have obtained an image twice the size of the object with a concave lens. Is he correct? Give a reason for your answer.
Kavita from 10th is using spectacles. The power of the lenses in her spectacles is –2.5 dioptre. Answer the following questions:
1) Which lenses are used in her spectacles?
2) State the defect of vision Kavita is suffering from.
3) Find the focal length of the lenses used in her spectacles
The lens A has a focal length of 25 cm whereas another lens B has a focal length of 60 cm. Giving reason state, which lens has more power: A or B.
Which type of lens has (a) a positive power, and (b) a negative power?
Which of the two has a greater power: a lens of short focal length or a lens of large focal length?
A converging lens has focal length of 50 mm. What is the power of the lens?
A doctor has prescribed a corrective lens of power, −1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?
What is the unit of power of a lens? Define the unit of power of a lens.
Define power of a lens. Write its units. Deduce the relation `1/f =1/f_1 +1/f_2`for two thin lenses kept in contact coaxially.
A 5.0 diopter lens forms a virtual image which is 4 times the object placed perpendicularly on the principal axis of the lens. Find the distance of the object from the lens.
A convex lens is of focal length 20 cm. Find its power.
The power of lens depends on the focal length of the lens
The focal length of a concave lens is 20 cm. The focal length of a convex lens is 25 cm. These two are placed in contact with each other. What is the power of the combination? Is it diverging, converging or undeviating in nature?
A convex lens with radii of curvature R1 = R2 is immersed in water. Assuming that the refractive indices of glass and water are 3/2 and 4/3 respectively, its focal length f1 in comparison to that in air, f, is ______.
A point object is placed at O in front of a glass sphere as shown in figure.
Show the formation of the image by the sphere.
The same size images are formed by a convex lens when the object is placed at 20 cm or at 10 cm from the lens. The focal length of convex lens is ______ cm.
The power of convex lens of focal length 20 cm is ______.
