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प्रश्न
Define 1 dioptre of power of a lens.
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उत्तर १
The SI unit of power of lens is dioptre which is denoted by the letter D. 1 dioptre is defined as the power of a lens of focal length 1 metre.
उत्तर २
1 dioptre is the power of a lens whose focal length is 1 metre.
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संबंधित प्रश्न
How unit of power related to focal length of a lens?
(a) At what distance should the lens be held from the figure in order to view the squares distinctly with the maximum possible magnifying power?
(b) What is the magnification in this case?
(c) Is the magnification equal to the magnifying power in this case? Explain.
What is the nature of a lens having a power of + 0.5 D?
What is the nature of a lens whose power is, −4 D?
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.
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?
What do you understand by the power of a lens? Name one factor on which the power of a lens depends.
What is the unit of power of a lens? Define the unit of power of a lens.
State the condition for the following a lens has both its focal lengths equal .
On reducing the focal length of a lens, its power ______.
Find the radius of curvature of the convex surface of a plano-convex lens, whose focal length is 0.3 m and the refractive index of the material of the lens is 1.5.
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
How is accommodation produced?
The following diagram shows the object O and the image I formed by a lens. Copy the diagram and on it mark the positions of the lens LL’ and focus (F). Name the lens.
Power of a lens is – 4D, then its focal length is
Match the following:
| Column - I | Column - II | ||
| 1 | Retina | a | Path way of light |
| 2 | Pupil | b | Far point comes closer |
| 3 | Ciliary muscles | c | near point moves away |
| 4 | Myopia | d | Screen of the eye |
| 5 | Hypermetropia | e | Power of accommodation |
Assertion and reasoning type
- Assertion: Myopia is due to the increase in the converging power of eye lens.
- Reason: Myopia can be corrected with the help of concave lens.
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 power of convex lens of focal length 20 cm is ______.
