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प्रश्न
Define power of a lens. What is its unit? One student uses a lens of focal length 50 cm and another of –50 cm. What is the nature of the lens and its power used by each of them?
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उत्तर
Power of a lens indicates the converging effect of the lens. It is the reciprocal of the focal length of the lens.
Mathematically, `"Power" ("P") = 1/"f"`
The unit of power is dioptre (D).
The nature and power of the lens in each case are:
When the focal length of the lens is 50 cm,
`("P") = 1/"f"`
`= 1/0.5`
= 2D
This lens has positive value of focal length. So, it is convex lens.
When the focal length of the lens is -50 cm,
`("P") = 1/"f"`
`= 1/(-0.5)`
= -2 D
This lens has negative value of focal length. So, it is concave lens.
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संबंधित प्रश्न
Define the power of a lens.
Give the usual name for the following:
A point inside a lens through which the light passes undeviated.
What is the power of a convex lens of focal length 0.5 m?
What is the power of a convex lens lens whose focal length is 80 cm?
The focal length of a lens is +150 mm. What kind of lens is it and what is its power?
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 ___________.
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 is the unit of power of a lens? Define the unit of power of a lens.
How does the power of a lens change if its focal length is doubled?
On reducing the focal length of a lens, its power ______.
A double convex lens has focal length 25 cm. The radius of curvature of one of the surfaces is double of the other. Find the radii, if the refractive index of the material of the lens is 1.5.
Which lens has more power a thick lens or a thin lens?
An object is placed in front of a converging lens. Obtain the conditions under which the magnification produced by the lens is
- negative and
- positive.
The power of a lens is defined as the:
The power of a lens in dioptres is given by:
The power of a lens placed in a medium is given by:
A concave lens is a diverging lens whose focal length and power are both:
A greater numerical value of the power of a lens means:
If the lens material and the surrounding liquid have the same refractive index (\[n_2 = n_1\]), then:
