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प्रश्न
What do you understand by the power of a lens? Name one factor on which the power of a lens depends.
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उत्तर
The power of a lens is a measure of the degree of convergence or divergence of light rays falling on it. It is defined as the reciprocal of the focal length of a lens in metres.
i.e., Power = `1/"focal length of lens (in metre)"`
Therefore, the power of a lens depends on the focal length.
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संबंधित प्रश्न
State power of a lens S.I. unit.
How unit of power related to focal length of a lens?
A student uses a lens of focal length 40 cm and another of –20 cm. Write the nature and power of each lens
What is the power of a convex lens of focal length 0.5 m?
Fill in the following blank with suitable word:
For converging lenses, the power is __________ while for diverging lenses, the power is ___________.
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.
A diverging lens has a focal length of 0.10 m. The power of this lens will be:
How is the sign (+ or -) of power of a lens related to its divergent or convergent action?
The power of a lens is + 1.0 D is :
How does focal length of a lens change when red light incident on it is replaced by violet light? Give reason for your answer.
Define power of a lens. Write its units. Deduce the relation `1/f =1/f_1 +1/f_2`for two thin lenses kept in contact coaxially.
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.
How is accommodation produced?
If the lens is of focal length 25 cm. Calculate the power of the lens.
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 |
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?
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 focal length of a double convex lens is equal to the radius of curvature of either surface. What is the refractive index of its material?
