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प्रश्न
How does the power of a lens change if its focal length is doubled?
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उत्तर
We know that
`"D"_1 = (100 " cm")/("F.L")` ...(i)
When focal length is doubled
`1"D"_2 = (100 " cm")/("2 F.L") = 50/"FL"` ...(ii)
`"D"_2/"D"_1 = 100/(2 "F.L") xx "F.L."/100 = 1/2`
`therefore "D"_2 = "D"_1/2`
∴ Power is Halved.
If the focal length of a lens is doubled, then its power gets halved.
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संबंधित प्रश्न
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Fill in the following blank with suitable word:
For converging lenses, the power is __________ while for diverging lenses, the power is ___________.
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Match the following:
| Column - I | Column - II | ||
| 1 | Retina | a | Path way of light |
| 2 | Pupil | b | Far point comes closer |
| 3 | Ciliary muscles | c | near point moves away |
| 4 | Myopia | d | Screen of the eye |
| 5 | Hypermetropia | e | Power of accommodation |
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