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A lens having focal length f and apertur...

A lens having focal length f and aperture of diameter `d//2` in the central region of the lens is covered by a black paper.Focal length of the lens and intensity of image image now will be respectively

A

f and `1//4`

B

`3 f//4` and `I//2`

C

`f and 3 I//4`

D

`f//2 and I//2`.

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MODERN PUBLICATION-UNIT TEST -06-EXERCISE
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  2. A luminous object is placed at a distance of 30 cm from the convex len...

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  3. A lens having focal length f and aperture of diameter d//2 in the cent...

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  4. A plano-convex lens is made of a material of refrative index mu=1.5.Th...

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  5. The radius of curvatrure of a thin plano-convex lens is 10 cm (of cur...

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  6. A convex lens is dipped in a liquid,whose refrctive index is equal to ...

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  7. If a convex lens of focal length 80 cm and a concave lens of focal len...

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  8. A convex lens and a concave lens ,each having same focal length of 25 ...

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  9. Two thin lenses of focal length f1 and f2 are in contact and coaxial.T...

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  10. A beam of light composed of red and greeen ray is incident obliquely a...

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  11. A ray light is incident on a 60^@ prism at the minimum deviation posit...

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  12. The refracting angle of a prism is 60^@ nd the refractive index of the...

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  13. A ray is incident at an angle of incidence i on one surface of a prism...

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  14. The refractive index of the amterial of a prism is sqrt2 and its refra...

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  15. The focal length of a coverging lens is measured for violet,green and ...

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  16. If fv and fr are the focal lengths of a convex lens fro violet and red...

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  17. Rainbow is formed due to combination fo

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  18. For relaxed eye,magnifying power of a microscope is

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

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  20. Which one off the following phenomena is not explained by Huygens' con...

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