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प्रश्न
What is the unit of power of a lens? Define the unit of power of a lens.
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उत्तर
The unit for the power of a lens is a dioptre (D). One dioptre is the power of a lens whose focal length is 1 metre.
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संबंधित प्रश्न
Calculate the focal length of a corrective lens having power +2D.
(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.
A converging lens has focal length of 50 mm. What is the power of the lens?
Fill in the following blank with suitable words :
The reciprocal of the focal length in metres gives you the _________ of the lens, which is measured in ___________.
Express the power (with sign) of a concave lens of focal length 20 cm.
Mohan obtained a sharp inverted image of a distant tree on the screen placed behind the lens. He then moved the screen and tried to look through the lens in the direction of the object. He would see:
(1) a blurred image on the wall of the laboratory.
(2) an erect image of the tree on the lens.
(3) no image as the screen has been removed
(4) an inverted image of the tree at the focus of the lens.
Consider three converging lenses L1, L2 and L3 having identical geometrical construction. The index of refraction of L1 and L2 are \[\mu_1 \text{ and } \mu_2\] respectively. The upper half of the lens L3 has a refractive index \[\mu_1\] and the lower half has \[\mu_2\] following figure . A point object O is imaged at O1 by the lens L1 and at O2 by the lens L2placed in same position. If L3 is placed at the same place,
(a) there will be an image at O1
(b) there will be an image at O2.
(c) the only image will form somewhere between O1 and O2
(d) the only image will form away from O2.
The power of a lens is +2.0 D. Find its focal length and state the kind of lens.
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If focal length of a convex lens is 20 cm at what is the power of the lens?
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.
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.
An object is kept at a distance of 1m from a lens of power +2D:
- Identify the type of lens.
- Calculate its focal length and distance of the image formed.
The lens of power + 1·0 D is ______.
The power of a lens is defined as the:
A convex lens is a converging lens whose focal length and power are both:
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A greater numerical value of the power of a lens means:
When a lens is placed in a liquid, light refracts at:
If the refractive index of the lens material is less than that of the surrounding liquid (\[n_2 < n_1\]), then:
