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A screen is placed 80 cm from an object....

A screen is placed 80 cm from an object. The image of the object on the screen is formed by a convex lens placed between them at two different locations separated by a distance 20 cm. Determine the focal length of the lens.

A

`D//a`

B

`D^2//a^2`

C

`sqrt(D//a)`

D

`(D-a)^2//(D+a)^2`.

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MODERN PUBLICATION-UNIT TEST -06-EXERCISE
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  2. The focal length of a convex lens is 30 cm and the size of image is qu...

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  3. A screen is placed 80 cm from an object. The image of the object on th...

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  4. Which of the following pairs can produce erect,diminshed and virutual ...

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  5. In order to obtain a real image of magnification 2 using a convergin l...

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  6. Which of the following is true for rays coming from infinity?

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  7. At what angle ,a ray of light will incident on one face of an equilate...

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  8. The blue colour of the sky is due to the phenomenon of

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  9. The sky appears blue, because.

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  10. A red piece of paper when illuminated by green light appears:

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  11. White light is passed through a dilute solution of potasssium permagna...

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  12. C.V. Raman received Nobel Prize for the discovery of the following phe...

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  13. C.V. Raman received Nobel Prize for the discovery of the following phe...

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  14. The formation of rainbow in due to the phenomenon of

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  15. If red light and violet light rays are of focal length fr adn fv then ...

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  16. A parallel beam of white ligth falls on a convex lens .Images of blue...

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  17. The dispersive powers of the materials of the two lenses are in the r...

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  18. Retina of eye corresponds to which part of camera?

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  19. The ability of eye-lens to adjust its focal length is called……. .

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  20. An astronomical telescope of ten fold angular magnification has a leng...

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