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A person who can see things most clearly...

A person who can see things most clearly at a distance of 10 cm , requires spectacles to be able to see clearly things at a distance of 30 cm . What should be the focal length of the spectacles ?

A

15 cm (concave)

B

15 cm (convex)

C

10 cm

D

zero

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The correct Answer is:
A
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CHHAYA PUBLICATION-OPTICAL INSTRUMENTS-Exercise(Multiple choice questions)
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  2. Ability of the eye to see objects at all distances is called

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  3. The numerical aperture for a human eye is of the order of

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  4. If there had been one eye of the man then

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  5. What type of lens should be used in spectacles for the remedy of myopi...

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  8. The image formed by the objective of a compound microscope is

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  9. To get a magnification from a compound microscope ,

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  10. The length of the tube a compound microscope is 21.5 cm . The focal l...

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  11. The angular magnification of a simple microscope can be increased by

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  12. The length of the tube of a microscope is 14 cm and its magnifying po...

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  13. A Galileo's telescope has an objective of focal length 100 cm and magn...

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  14. In a Galileo's telescope , the inverted image formed by its objective...

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  15. In an astromical telescope , if the focal lengths of the objective an...

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  16. In case of normal focussing of an astronomical telescope the final ima...

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  17. The angular magnification of an astronomical telescope will be maximum...

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  18. If the focal length of the eyepiece of a telescope is doubled, its mag...

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