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Two lenses, one diverging of power 2 dio...

Two lenses, one diverging of power 2 diopyre and the other converging of power `6 dioptre` are combined together. Calculate focal length and power of the combination.

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The correct Answer is:
25 cm, 4 D
Here, `P_1 = -2 D P_1 = + 6 D`
Power of combination,
`P = P_1 + P_2 = -2 + 6 = 4 D`
`F = (100)/(P) = (100)/(4) = 25 cm`.
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PRADEEP-RAY OPTICS-Problem For Practice(b)
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  2. The image obtained with a convex lens is erect and its length is 4 tim...

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  3. An illuminated object and a screen are placed 90 cm apart. What is the...

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  4. A convex lens of focal length 25 cm is placed co-axially in contact wi...

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  5. The radius of curvature of the faces of a double convex lens are 10 cm...

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  6. A biconvex lens has focal length (2)/(3) times the radius of curvature...

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  7. An object is placed at a distance of 1.5 m from a screen and a convex ...

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  8. Find the focal length and power of a convex lens, which when placed in...

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  9. Find the focal length and nature of lens which should be placed in con...

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  10. Two lenses, one diverging of power 2 diopyre and the other converging ...

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  11. Two lenses of power + 10 D and - 5 D are placed in contact, (i) Calc...

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  12. A point object is placed 60 cm in front of a convex lens of focal leng...

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  13. A convex lens of focal length 15 cm, and a concave mirror of radius of...

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  14. Fig. shows a plane mirror M placed at a distance of 10 cm from a conca...

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  15. Monochramatic light is incident on the pLane interface AB between two ...

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  16. The image of a needle placed 45 cm from a lens is formed on a screen p...

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  17. A biconvex thin lens is prepared from glass (mu=1.5), the two bounding...

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  18. A concave convex figure lens made of glas (mu=1.5) has surface of radi...

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  19. A converging beam of light forms a sharp image on a screen. A lens is ...

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  20. Rays of light are falling on a convex lens of focal length 40 cm. As s...

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