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A convex lens has 20 cm focal length in ...

A convex lens has 20 cm focal length in air. What is focal length in water? (Refractive index of air-water = 1.33, refractive index for air-glass = 1.5.)

A

39.1 cm

B

156.4 cm

C

78.2 cm

D

`20.0` cm

Text Solution

Verified by Experts

The correct Answer is:
C
78.2 cm
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KUMAR PRAKASHAN-RAY OPTICS AND OPTICAL INSTRUMENTS-SECTION-D (MULTIPLE CHOICE QUESTIONS (MCQs))(MCQs FROM .DARPAN. BASED ON TEXTBOOK)(MCQs BASED ON TEXTUAL ILLUSTRATION AND EXERCISE)
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  2. (i) If f = 0.5 m for a glass lens, what is the power of the lens? (ii)...

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  3. A convex lens has 20 cm focal length in air. What is focal length in w...

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  4. A small candle, 2.5 cm in size is placed at 27 cm in front of a concav...

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  5. A 4.5 cm needle is placed 12 cm away from a convex mirror of focal len...

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  6. A tank is filled with water to a height of 12.5 cm. The apparent depth...

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  7. A small bulb is placed at the bottom of a tank containing water to a d...

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  8. Double-convex lenses are to be manufactured from a glass of refractive...

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  9. What is the focal length of a convex lens of focal length 30cm in cont...

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  10. A small telescope has an objective lens of focal length 144cm and an e...

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  11. (a) A giant refracting telescope at an observatory has an objective le...

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  12. (a) A giant refracting telescope at an observatory has an objective le...

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  13. A small pin fixed on a table top is viewed from above from a distance ...

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  14. The image of a small electric bulb fixed on the wall of a room is to b...

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  16. At what angle should a ray of light be incident on the face of a prism...

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  17. A small telescope has an objective lens of focal length 140cm and an e...

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  18. A small telescope has an objective lens of focal length 140cm and an e...

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  19. For the telescope described in Exercise 9.3 (a), what is the separatio...

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  20. If this telescope is used to view a 100 m tall tower 3 km away, what i...

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