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प्रश्न
What does sign of power (+ve or –ve) indicate?
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उत्तर
Positive power (+ve) of a lens indicates converging ability of a lens as in the case of convex lens, and negative power (−ve) of a lens indicates its diverging ability as in the case of concave lens.
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संबंधित प्रश्न
What can you see in a completely dark room? If you switch on an electric bulb in this dark room as a light source, explain how you could now see:
(a) the electric bulb
(b) a piece of white paper
The power of a lens is + 0.2 D. Calculate its focal length.
An object of height 4.25 mm is placed at a distance of 10 cm from a convex lens of power +5D. Find (i) the focal length of the lens, and (ii) the size of the image.
Express the power (with sign) of a concave lens of focal length 20 cm.
Consider the situation described in the previous problem. Where should a point source be placed on the principal axis so that the two images form at the same place?
Which lens has more power a thick lens or a thin lens?
Focal length : metre : : power of lens : _______
Find the power of a convex lens of focal length of + 25 cm.
Assertion and reasoning type
- Assertion: Myopia is due to the increase in the converging power of eye lens.
- Reason: Myopia can be corrected with the help of concave lens.
In what unit is the power of a lens expressed?
