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प्रश्न
Differentiate convex lens and concave lens.
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उत्तर
| Convex Lens | Concave Lens |
| 1. The lens which is thicker at the centre than at the edges. | 1. The lens is thinner at the centre than at the edges. |
| 2. Abeam of light passing through it, is converged to a point. | 2. A beam of light passing through it is diverged or spread out. |
| 3. It is called a converging lens. | 3. It is called a diverging lens. |
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संबंधित प्रश्न
Analyse the following observation table showing variation of image-distance (v) with object-distance (u) in case of a convex lens and answer the questions that follow without doing any calculations :
| S. No. | Object-Distance u (cm) |
Image-Distance v (cm) |
| 1 | –100 | +25 |
| 2 | –60 | +30 |
| 3 | –40 | +40 |
| 4 | –30 | +60 |
| 5 | –25 | +100 |
| 6 | –15 | +120 |
(a) What is the focal length of the convex lens? Give reason to justify your answer.
(b) Write the serial number of the observation which is not correct. On what basis have you arrived at this conclusion?
(c) Select an appropriate scale and draw a ray diagram for the observation at S.No. 2. Also find the approximate value of magnification.
Describe with the help of a ray diagram the nature, size and position of the image formed when an object is placed in front of a convex lens between focus and optical centre. State three characteristics of the image formed.
With the help of a labelled diagram explain how a convex lens converges a beam of parallel light rays. Mark the principal axis, optical centre, principal focus and focal length of the convex lens on the diagram.
Find the nature, position and magnification of the images formed by a convex lens of focal length 0.20 m if the object is placed at a distance of:
0.15 m
What type of images can a convex lens make?
In a certain murder investigation, it was important to discover whether the victim was long-sighted or short-sighted. How could a detective decide by examining his spectacles?
A parallel oblique beam of light falls on a convex lens. Draw a diagram to show the refraction of light through the lens.
Answer the following question.
List four precautions which a student should observe while determining the focal length of a given convex lens by obtaining an image of a distant object on a screen.
Distinguish between:
Concave lens and Convex Lens
Distinguish between Concave lens and Convex Lens.
