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A candle is placed 15cm in front of a le...

A candle is placed 15cm in front of a lens. If the image of the candle captured on a screen is magnified two time, calculate the focal length and nature of the lens.

Text Solution

Verified by Experts

Here, `u=-15cm,m=-2` (Note the negative sign. As the image is on a screen, it is real which implies m must be negative)
`:. v=m u=+30cm`
Applying equation, we get
`(1)/(f)=(1)/(30)-(1)/(-15)` or `f=10cm`
Therefore, the lens is convex, with focal length of 10cm.
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