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A lens made of glass whose index of refr...

A lens made of glass whose index of refraction is 1.60 has a focal length of + 20 cm in air. Its focal length in water, whose refractive index is 1.33, will be

A

three times longer than in air

B

two times longer than in air

C

same as in air

D

None of these

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The correct Answer is:
A
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DISHA PUBLICATION-RAY OPTICS AND OPTICAL INSTRUMENTS-Exercise - 1 : Concept Builder (Topicwise)(Topic 3 : Refraction of light at Spherical Surface and Power of Lens)
  1. A point object is placed at the centre of a glass sphere of radius 6cm...

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  2. A parallel beam of light is incident on the surface of a transparent h...

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  3. A lens made of glass whose index of refraction is 1.60 has a focal len...

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  4. A convex lens is in contact with a concave lens. The magnitude of the ...

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  5. A parallel beam of light is incident on a converging lens parallel to ...

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  6. A converging beam of rays in incident on a diverging lens. Having pass...

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  7. A body is located on a wall. Its image of equal size is to be obtained...

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  8. A luminous object is placed at a distance of 30 cm from the convex len...

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  9. A plano-convex lens fits exactly into a plano-concave lens. Their plan...

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  10. A plano concave lens is placed on a paper on which a flower is drawn. ...

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  11. A drop of water is placed on a glass plate. A double convex lens havin...

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  12. A point object O is placed in front of a glass rod having spherical en...

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  13. A spherical surface of radius of curvature R separates air (refractive...

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  14. A convex lens of focal length 40 cm is held coaxially 12 cm above a mi...

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  15. A point object is placed at a distance of 20 cm from a thin plano-conv...

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