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Explain first focal centre and second fo...

Explain first focal centre and second focal centre for lens.

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(i) First focal point : Position of object from which image formed by lens at infinity is called first focal point `(F_1)`.

Second focal point : Position of point like image formed by lens for object at infinity is called second focal point `(F_2)`.
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KUMAR PRAKASHAN-RAY OPTICS AND OPTICAL INSTRUMENTS-SECTION-D (MULTIPLE CHOICE QUESTIONS (MCQs))(MCQs ASKED IN COMPETITIVE EXAMS)
  1. Explain first focal centre and second focal centre for lens.

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  2. Which of the following is used in optical fibres ?

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  3. An astronomical telescope has a large aperture to ….. .

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  4. If two mirrors are kept at 60^@ to each other, then the number of imag...

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  5. As shown in figure, a plano-convex lens of focal length 20 cm is silve...

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  6. A light ray is incident perpendicular to one face of a 90^@ prism and ...

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  7. A plano- convex lens of refractive index 1.5 and radius of curvature 3...

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  8. The refractive index of transparent cylindrical rod is (2)/(root3) . A...

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  9. A fish looking up through the water sees the outside world, contained ...

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  10. Two point white dots are 1 mm apart on a black paper. They are viewed ...

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  11. A thin glass (refractive index 1.5) lens has optical power of - 5D in ...

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  12. The refractive index of glass is 1.520 for red light and 1.525 for blu...

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  13. Two lenses of power - 15D and + 5D are in contact with each other. The...

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  14. When monochromatic red light is used instead of blue light in a convex...

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  15. A beaker contains water up to a height h(1) and kerosene of height h(2...

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  16. Diameter of a plano-convex lens is 6 cm and thickness at the centre is...

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  17. A green light is incident from the water to the air-water interface at...

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  18. Monochromatic light is incident on a glass prism of angle A. If the re...

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  19. On a hot summer night, the refractive index of air is smallest near th...

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  20. An observer looks at a distant tree of height 10 m with a telescope of...

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  21. A diverging lens with magnitude of focal length 25 cm is placed at a d...

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