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प्रश्न
Distinguish between concave and convex lens.
उत्तर
| Convex lens | Concave lens |
| 1. A convex lens is thicker in the middle and thinner at its edges. | 1. A concave lens is thicker at the edges and thinner in the middle |
| 2. A light beam converges on passing through a convex lens. | 2. A light beam diverges on passing through a concave lens. |
| 3. The convex lens produces a real image that is inverted and is smaller and can be obtained on screen. | 3. A concave lens always forms a virtuall image, the image is magnified and cannot be obtaiined on screen. |
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संबंधित प्रश्न
A converging lens is used to produce an image of an object on a screen,object on a screen. What change is needed for the image to be formed nearer to the lens?
(a) increase the focal length of the lens
(b) insert a diverging lens between the lens and the screen
(c) increase the distance of the object from the lens
(d) move the object closer to the lens
How would you alter the above diagram to show how a converging lens can produce a beam of parallel rays of light.
Copy and complete the diagram below to show what happens to the rays of light when they pass through the concave lens:
When an object is kept at any distance in front of a concave lens, the image formed is always:
(a) virtual, erect and magnified
(b) virtual, inverted and diminished.
(c) virtual, erect and diminished
(d) virtual, erect and same size as object
Which of the following can form a virtual image which is always smaller than the object?
(a) a plane mirror
(b) a convex lens
(c) a concave lens
(d) a concave mirror
An object 60 cm from a lens gives a virtual image at a distance of 20 cm in front of the lens. What is the focal length of the lens? Is the lens converging or diverging? Give reasons for your answer.
The power of a concave lens is 10 D and that of a convex lens is 6 D. When these two lenses are placed in contact with each other, the power of their combination will be :
(a) +16 D
(b) +4 D
(c) −16 D
(d) −4 D
Out of the two lenses, one concave and the other convex, state which one will show the divergent action on a light beam. Draw diagrams to illustrate your answer.
The power of a lens is negative. State whether it is convex or concave.
At what distance from a concave lens of focal length 20 cm a 6 cm tall object be placed so as to obtain its image at 15 cm from the lens? Also calculate the size of the image formed.
Draw a ray diagram to justify your answer for the above situation and label it.
