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A concave lens is placed in contact with...

A concave lens is placed in contact with a convex lens of focal length 25 cm.The combination produces a real image at adistance of 80 cm, when an object is at a distance of 40 cm. What is the focallength of concave lens ?

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PUNJAB BOARD PREVIOUS YEAR PAPERS-Refraction of Light and Lenses-EXERCISE
  1. The radii of curvature of the faces of a double convex lens are 10 cm ...

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  2. A convex lens has 20 cm focal length in air.What is its focal length i...

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  3. A concave lens is placed in contact with a convex lens of focal length...

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  4. A convex lens has 10 cm focal length in air.What is its focal length i...

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  5. A concave lens is kept in contact with convex lens of focal length 20 ...

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  6. A convex lens is made of glass of refractive index 1.5. If radius of c...

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  7. A needle placed 45cm from a lens forms an image on the screen placed 9...

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  8. A lens of focal length 12 cm produces a virtual image. The size of ima...

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  9. The image formed by the lens is erect and its length is three times th...

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  10. A lens placed at a distance of 20 cm from an object produces a virtual...

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  11. A needle placed 40 cm from a lens forms an image on a screen placed 80...

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  12. What is the focal lengthof the combination of a convex lens of focal l...

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  13. An object of size 5 cm is placed at distance of 25 cm in front of a co...

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  14. An object of size 10 cm is placed at distance of 20 cm in front of aco...

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  15. Two lenses of powers+15D and -5D are in contact with each other. What ...

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  16. If the focal length of a converging lens is 50 cm. What is the power o...

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  17. Define refractive index?

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  18. State Snell's law of refraction of light.

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  19. What is refraction of light?

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  20. A convex lens made of a material of refractive index mu1 , is kept in ...

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