Q24 of 36 Page 379

What is meant by ‘power of a lens’?

Power of lens is defined as the efficiency with which a lens can converge or diverge the light ray.

P (in dioptre) =


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22

What is meant by power of a lens? Name and define its S.I. unit.

One student uses a lens of focal length +50 cm and another of –50cm. State the nature and find the power of each lens. Which of the two lenses will always give a virtual, erect and diminished image irrespective of the position of the object?

 23

A 5 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 18 cm at a distance of 12 cm from it. Use lens formula to determine the position, size and nature to the image formed.

 24

State and define the S.I. unit of power of a lens.

 24

A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are placed in close focal contact with each other. Calculate the lens power of this combination.