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प्रश्न
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 ___________.
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उत्तर
The reciprocal of the focal length in metres gives you the power of the lens, which is measured in dioptres.
संबंधित प्रश्न
What is meant by a power of a lens? Define its SI unit.
What does sign of power (+ve or –ve) indicate?
A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the 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.
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.
The lens mentioned in 6(b) above is of focal length 25cm. Calculate the power of the lens.
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 of the two has a greater power: a lens of short focal length or a lens of large focal length?
How is the power of a lens related to its focal length?
The focal length of a convex lens is 25 cm. What is its power?
A converging lens has focal length of 50 mm. What is the power of the lens?
What is the nature of a lens having a power of + 0.5 D?
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?
A lens has a focal length of, −10 cm. What is the power of the lens and what is its nature?
A combination of lenses for a camera contains two converging lenses of focal lengths 20 cm and 40 cm and a diverging lens of focal length 50 cm. Find the power and focal length of the combination.
A converging lens has a focal length of 50 cm. The power of this lens is:
Define the term focal length of a lens.
State the condition for the following a lens has both its focal lengths equal .
State the condition for the following a ray passes undeviated through the lens .
The power of a lens is + 1.0 D is :
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 thin converging lens is formed with one surface convex and the other plane. Does the position of image depend on whether the convex surface or the plane surface faces the object?
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 |
When monochromatic red light is used instead of blue light in a convex lens, its focal length will ______.
The power of convex lens of focal length 20 cm is ______.
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 power of a lens is defined as the:
A negative power of a lens indicates a:
