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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
State whether convex lens has a real focus or a virtual focus.
Three convex lenses are available having focal lengths of 4 cm, 40 cm and 4 m respectively. Which one would you choose as a magnifying glass and why?
An object 2 cm tall is placed on the axis of a convex lens of focal length 5 cm at a distance of 10 m from the optical centre of the lens. Find the nature, position and size of the image formed. Which case of image formation by convex lenses is illustrated by this example?
What type of lens is used to correct
hypermetropia
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 | –60 | +12 |
| 2 | –30 | +15 |
| 3 | –20 | +20 |
| 4 | –15 | +30 |
| 5 | –12 | +60 |
| 6 | –9 | +90 |
(a) What is the focal length of the convex lens? State reason for your answer.
(b) For what object-distance (u) is the corresponding image-distance (v) not correct? How did you arrive at this conclusion?
(c) Choose an appropriate scale to draw a ray diagram for the observation at S. No. 4 and find the approximate value of magnification.
Out of the five incident rays shown in the figure find the three rays that are obeying the laws of refraction and may be used for locating the position of image formed by a convex lens:
(A) 1, 2 and 3
(B) 2, 3 and 4
(C) 3, 4 and 5
(D) 1, 2 and 4
Draw neat diagram to show the
Convergent action of a convex lens,
State the position of object, position of image, nature of image when: Convex lens is used as an erecting lens in terrestrial telescope.
Define the principal focus of a convex lens.
Distinguish between:
Concave lens and Convex lens
