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प्रश्न
Which type of lenses are:
thinner in the middle than at the edges?
उत्तर
A concave lens is thinner in the middle than at the edges.
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संबंधित प्रश्न
Define the principal focus of a concave lens.
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
Fill in the following blank with suitable word:
A convex lens .................. rays of light, whereas a concave lens .................. rays of light.
When an object is placed 10 cm in front of lens A, the image is real, inverted, magnified and formed at a great distance. When the same object is placed 10 cm in front of lens B, the image formed is real, inverted and same size as the object.
What is the focal length of lens B?
An object is placed at a distance of 4 cm from a concave lens of focal length 12 cm. Fine the position and nature of the image.
(a) Find the position and size of the virtual image formed when an object 2 cm tall is placed 20 cm from:
(i) a diverging lens of focal length 40 cm.
(ii) a converging lens of focal length 40 cm.
(b) Draw labelled ray diagrams to show the formation of images in case (i) and (ii) above (The diagrams may not be according to scale).
- Name the lens which always forms an erect and virtual image.
- State whether the image in part (a) is magnified or diminished.
Copy the following figure and complete it to show the formation of the image of the object AB. Name the lens used in the figure.
Draw images in case of a concave lens when the object is at infinity.
Distinguish between:
Concave Lens and Convex Lens
