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Two thin lenses of focal lengths f1, and...

Two thin lenses of focal lengths `f_1`, and `f_2` are placed co-axially in contact. The combination acts as a single lens of focal length

A

`(f_1f_2)/(f_1+f_2)`

B

root(f1.f2)

C

`(f_1+f_2`)/(f1.f2)`

D

`(f_1+f_2)/2`

Text Solution

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The correct Answer is:
A
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BINA LIBRARY-Optics-I-EXERCISE
  1. Radius of curvature of a convex mirror is 40 cm and the size of the ob...

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  2. A convex lens has a focal length f. It is cut into two parts along a l...

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  3. Two thin lenses of focal lengths f1, and f2 are placed co-axially in ...

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  4. The plane surface of a plano convex lens of focal length f is silvered...

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  5. The magnifying power of a telescope is m. If the focal length of the e...

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  6. When red glass is heated in a dark room it seems

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  7. Focal length of a convex lens will be maximum for

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  8. Rainbow is due to a combination of

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  9. An astronaut in a spaceship sees the sky as

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  10. The sky looks blue due to-

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  11. A convex lens of focal length 0.5 m and a concave lens of focal length...

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  12. An enlarged virtual image can be obtained only in

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  13. A convex mirror gives images which are

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  14. A vitrual image larger than the object can be produced by

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  15. A concave mirror forms an image of a real object. Which statement is w...

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  16. Give reasons why convex mirrors are generally used as driving mirrors.

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  17. The image of an object placed between the principal focus and the cent...

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  18. The distance of an object and its image from the focus of a concave mi...

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  19. An inverted image can be seen in a convex mirror

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  20. A concave mirror produces a virtual image when the object is

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