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A professor reads a greeting card receiv...

A professor reads a greeting card received on his 50th birthday with + 2.5 D glasses keeping the card 25 cm away. Ten years later, he reads his farewell letter with the same glasses but he has to keep the letter 50 cm away. What power of lens should he now use?

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D
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HC VERMA-OPTICAL INSTRUMENTS-Exercises
  1. A simple microscope is rated 5 X for a normal relaxed eye. What Will b...

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  2. Find the maximum magnifying power of a compound microscope having a 25...

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  3. The separation between the objective and the eyepiece of a compound mi...

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  4. In a compound microscope, the objective and eyepiece have focal length...

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  5. A compound microscope has a magnifying power of 100 when the image is ...

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  6. A compound microphone has an objective of focal length 1 cm and an eye...

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  7. An optical instrument used for angular magnification has a 25 D object...

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  8. An astronimical telescope is to be designed to have a magnifying power...

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  9. The eyepice of an astronomicasl telescope has a focasl length of 10 cm...

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  10. A Galilean telescope is 27 cm long when focussed to form an image at i...

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  11. A farsighted person cannot see objects placed closer to 50 cm. Find th...

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  12. A nearsighted person cannot clearly see beyond 200 cm. Find the power ...

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  13. A person wears glasses of power - 2.5 D. Is the person short sighted o...

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  14. A professor reads a greeting card received on his 50th birthday with +...

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  15. A normal eye has retina 2 cm behind the eye-lens. What is the power of...

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  16. The near point and the far point of a child are at 10 cm and 100 cm. I...

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  17. A nearsighted person cannot see beyond 25 cm. Assuming that the separa...

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  18. A person has near point at 100 cm. What power of lens is needed to rea...

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  19. A lady uses + 1.5 D glasses to have normal vision from 25 cm onwards. ...

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  20. A lady cannot see objects closer than 40cm from the left eye and close...

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