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प्रश्न
A 50 cm tall object is at a very large distance from a diverging lens. A virtual, erect and diminished image of the object is formed at a distance of 20 cm in front of the lens. How much is the focal length of the lens?
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उत्तर
Since the object is at infinity, the image will be formed at the focus. The image distance will be equal to the focal length of the lens. Therefore, the focal length of the lens is 20 cm.
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संबंधित प्रश्न
Explain the following term related to spherical lenses:- principal axis
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Image formed by a convex ______ is always virtual and smaller in size.
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front side of a shining steel spoon?
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Name the spherical mirror which can produce a virtual and diminished image of an object.
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What will be the focal length of this mirror?
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(A) Convex mirror of focal length 12 cm
(B) Convex lens of focal length 24 cm
(C) Concave mirror of focal length 24 cm
(D) Convex lens of focal length 12 cm
AB and CD, two spherical mirrors, from parts of a hollow spherical ball with its centre at O as shown in the diagram. If arc AB = `1/2` arc CD, what is the ratio of their focal lengths? State which of the two mirrors will always form virtual image of an object placed in front of it and why.
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(A) Should move the mirror away from the screen.
(B) Should move the mirror towards the screen.
(C) Should move the mirror and screen both towards the sun.
(D) Should move only the screen towards the sun.
What is a spherical mirror?
State whether the image in part (a) is real or virtual?
Name the kind of mirror used to obtain :
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- the position of the image
- the focal length of the convex mirror.
Define the following term:
concave mirror
Define the term principal focus in case of convex mirror. Draw a convex mirror and show its principal focus and focal length clearly.
