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प्रश्न
A symmetric double convex lens in cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4 D, the power a cut-lens will be
पर्याय
2 D
3 D
4 D
5 D.
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उत्तर
2 D
The lens is cut into two equal parts by a plane perpendicular to the principal axis. Thus, the radius of curvature of both the lenses become half of its original value.
As,
\[f = \frac{R}{2}\]
\[P = \frac{1}{f}\]
Radius of curvature becomes half. Therefore, the focal also
reduces to half its original value.
Thus, the power (P) of the two cut-lenses will be equal.
2 P = 4 D
P = 2 D
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संबंधित प्रश्न
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How unit of power related to focal length of a lens?
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Name the physical quantity whose unit is dioptre.
How is the power of a lens related to its focal length?
What is the nature of a lens whose power is, −4 D?
An object of height 4 cm is placed at a distance of 15 cm in front of a concave lens of power, −10 dioptres. Find the size of the image.
An object of height 4.25 mm is placed at a distance of 10 cm from a convex lens of power +5D. Find (i) the focal length of the lens, and (ii) the size of the image.
The power of a combination of two lenses X and Y is 5 D. If the focal length of lens X be 15 cm :
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(c) What is the power of combination if lenses A and B are held close together?
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Consider the situation described in the previous problem. Where should a point source be placed on the principal axis so that the two images form at the same place?
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Complete the diagram to show the formation of the image of the object AB.
(i) Name the Lens LL’.
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(iii) State three characteristics of the image.
If the lens is of focal length 25 cm. Calculate the power of the lens.
Focal length : metre : : power of lens : _______
In what unit is the power of a lens expressed?
