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A convex lens of focal length 80 cm and ...

A convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined toghether. What will be their resulting power ?

A

`45`

B

`30`

C

`15`

D

`5`

Text Solution

Verified by Experts

The correct Answer is:
D
`(1)/(f)=(1)/(f_(1))+(1)/(f_(2))-(d)/(f_(1)f_(2))=0`
`= (1)/(25)+(1)/(-20)-(d)/(-500)=0=(20-25)/(500)=-(d)/(500)`
`d=5 cm`
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RESONANCE ENGLISH-GEOMATRICAL OPTICS -Exercise-1
  1. Define: Radius of curvature and centre of curvature

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  2. The focal length of a plano-concave lens is -10 cm , then its focal le...

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  3. A convex lens of focal length 80 cm and a concave lens of focal length...

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  4. The dispersion of light in a medium implies that :

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  5. Critical angle of light passing from glass to air is least for

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  6. A plane glass slab is placed over various coloured letters. The letter...

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  7. A medium has nv = 1.56, nr=1.44. Then its dispersive power is:

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  8. All the listed things below are made of flint glass. Which one of thes...

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  9. Light of wavelenght 4000 A is incident at small angle on a prim of ape...

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  10. A simple microscope has a focal length of 5 cm . The magnification at...

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  11. In a compound microscope, the intermediate image is

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  12. The resolving power of a telesope is more when its objective lens has

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  13. A Galileo telescope has an objective of focal length 100cm and magnif...

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  14. The convex lens is used in-

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  15. The magnifying power of a simple microscope can be increased, if we us...

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  16. The focal length of the objective lens of a compound microscope is

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  17. Resolving power of a microscope is given by

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  18. An astronomical telescope has an eyepiece of focal-length 5cm. If the ...

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  19. A person with a defective sight is using a lens having a power of +2D....

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  20. The focal lengths of the objective and eye lens of a microscope are 1 ...

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