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A magician during a show makes a glass lens with n=1.47 disappear in the trough of liquid. What is the refractive index of the liquid.

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The refractive index of the liquid must be equal to 1.47 in order to make the lens disappear. This means` n_(1) = n_(2)` . This gives `1//f =0 or f rarr oo`. The lens in the liquid will act like a plane sheet of glass. No, the liquid is not water. It could be glycerine.
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NCERT GUJARATI-RAY OPTICS AND OPTICAL INSTRUMENTS-EXERCISES
  1. A magician during a show makes a glass lens with n=1.47 disappear in t...

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

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

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

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  5. Figures 9.31(a) and (b) show refraction of a ray in air incident at 60...

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

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  7. A prism is made of glass of unknown refractive index. A parallel beam ...

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

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  9. A beam of light converges at a point P. Now a lens is placed in the pa...

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  10. An object of size 3.0cm is placed 14cm in front of a concave lens of f...

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

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  12. A compound microscope consists of an objective lens of focal length 2....

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  13. A person with a normal near point (25 cm) using a compound microscope ...

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

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

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  16. Use the mirror equation to deduce that: (a) an object placed between...

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

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  18. (a) Figure 9.32 shows a cross-section of a 'light pipe' made of a glas...

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  19. Answer the following questions: (a) You have learnt that plane and c...

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  20. Answer the following questions: (b) A virtual image, we always say, ...

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  21. Answer the following questions: (c) A diver under water, looks obliq...

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