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प्रश्न
Define the power of a lens.
Define the term power of a lens.
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उत्तर १
Power of a lens is defined as the ability of a lens to bend the rays of light. It is given by the reciprocal of focal length in metre.
उत्तर २
The power of a lens is a measure of the deviation produced by it in the path of rays refracted through it.
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संबंधित प्रश्न
State power of a lens S.I. unit.
Define 1 dioptre of power of a lens.
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.
Find the power of a concave lens of focal length 2m.
The lens mentioned in 6(b) above is of focal length 25cm. Calculate the power of the lens.
Kavita from 10th is using spectacles. The power of the lenses in her spectacles is –2.5 dioptre. Answer the following questions:
1) Which lenses are used in her spectacles?
2) State the defect of vision Kavita is suffering from.
3) Find the focal length of the lenses used in her spectacles
How is the power of a lens related to its focal length?
A diverging lens has focal length of 3 cm. Calculate the power.
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?
The power of a lens is +2.0D. Its focal length should be :
On reducing the focal length of a lens, its power ______.
How does focal length of a lens change when red light incident on it is replaced by violet light? Give reason for your answer.
A double convex lens has two surfaces of equal radii R and refractive index \[m = 1 \cdot 5\]
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.
Complete the diagram to show the formation of the image of the object AB.
(i) Name the Lens LL’.
(ii) Where is the image of the object AB formed?
(iii) State three characteristics of the image.
If focal length of a convex lens is 20 cm at what is the power of the lens?
Increase in the converging power of eye lens cause ‘hypermetropia'
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 power of convex lens of focal length 20 cm is ______.
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?
