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Question
Differentiate convex lens and concave lens.
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Solution
| 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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RELATED QUESTIONS
A student places a candle flame at a distance of about 60 cm from a convex lens of focal length 10 cm and focuses the image of the flame on a screen. After that he gradually moves the flame towards the lens and each time focuses the image on the screen.
(a) In which direction-toward or away from the lens, does he move the screen to focus the image?
(b) How does the size of the image change?
(c) How does the intensity of the image change as the flame moves towards the lens?
(d) Approximately for what distance between the flame and the lens, the image formed on the screen is inverted and of the same size?
Describe the nature of image formed when an object is placed at a distance of 30 cm from a convex lens of focal length 15 cm.
A beam of parallel light rays is incident through the holes on one side of a box and emerges out through the holes on its opposite side as shown in the diagram below:
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(c) a convex lens
(d) a glass prism
Study the diagram given below.

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Study the diagram below.

what are the points O, O’ called?
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draw suitable rays to locate the lens and its focus.
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_______ times larger images can be obtained by using a simple microscope.
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Concave lens and Convex Lens
