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The dispersive powers of crown and flint...

The dispersive powers of crown and flint glasses are `0.02` and `0.04` respectively. In an achromatic combination of lenses the focal length of flint glass lens is `40 cm`. The focal length of crown glass lens will be

A

`-20 cm`

B

`+20 cm`

C

`-10 cm`

D

`+10 cm`

Text Solution

Verified by Experts

The correct Answer is:
A
`(omega_(1))/(f_(1)) +(omega_(2))/(f_(2)) = 0 rArr (0.02)/(f_(1)) +(0.04)/(40) = 0`
`f_(1) =- 20cm`
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CP SINGH-OPTICAL INSTRUMENTS-EXERCISES
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  2. Mark the correct options (i) If the far point goes ahead, the power ...

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  4. Astigmatism for a human eye can be removed by using

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  5. A man, wearing glasses of power +2D can read clearly a book placed at ...

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  6. A person whose far-point is at 30cm wants to read at 50cm. The power o...

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  7. A person wears glasses of power -2.5D. The defect of the eye and the f...

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  8. A far-sighted man can see clearly at a distance of 1.0m. The power of ...

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  9. The near point of a person is 50 cm and the far point is 1.5m. The spe...

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  10. An eye specialist prescribes spectacles having combination of convex l...

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  11. How should people wearing spectacles work with a microscope

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  12. Chromatic aberrations in the formation of image by a lens arise becaus...

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  13. Which of the following quantities related to a lens depend on the wave...

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  14. Let f(v) and f(r) are the focal lengths of a convex lens for violet an...

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  15. An achromaic convergent system of focal length +20cm is made of two le...

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  16. A combination of two thin lenses of the same material with focal lengt...

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  17. The dispersive powers of crown and flint glasses are 0.02 and 0.04 res...

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  18. The dispersive power of the material of lens of focal length 20cm is 0...

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  19. Spherical aberration in a thin lens can be reduced by

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  20. Spherical aberration in a lens

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