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Define the power of a lens. - Science

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प्रश्न

Define the power of a lens.

Define the term power of a lens.

व्याख्या
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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.

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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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  या प्रश्नात किंवा उत्तरात काही त्रुटी आहे का?
पाठ 4: Refraction through Lenses and Optical Instruments - Short Answers

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आईसीएसई Physics [English] Class 10
पाठ 4 Refraction through Lenses and Optical Instruments
Short Answers | Q 2
सेलिना Physics [English] Class 10 ICSE
पाठ 5 Refraction through a Lens
EXERCISE - 5 (C) | Q 6. (a) | पृष्ठ १२६

संबंधित प्रश्‍न

What does sign of power (+ve or –ve) indicate?


How unit of power related to focal length 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.


What can you see in a completely dark room? If you switch on an electric bulb in this dark room as a light source, explain how you could now see:
(a) the electric bulb
(b) a piece of white paper


What is the nature of a lens having a power of + 0.5 D?


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 do you understand by the power of a lens? Name one factor on which the power of a lens depends.


A diverging lens has a focal length of 0.10 m. The power of this lens will be:


The power of a lens is +2.0D. Its focal length should be :


On reducing the focal length of a lens, its power ______.


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 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.


A convex lens is of focal length 20 cm. Find its power.


The power of lens depends on the focal length of the lens


The same size images are formed by a convex lens when the object is placed at 20 cm or at 10 cm from the lens. The focal length of convex lens is ______ cm.


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