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Question
An object is placed at a distance 24 cm in front of a convex lens of focal length 8 cm.
(i) What is the nature of the image so formed?
(ii) Calculate the distance of the image from the lens.
(iii) Calculate the magnification of the image.
Solution
(i) As for convex lens, if |u| > | f | then real and inverted image is formed and as |u| > 2| f | then it is diminished.
(ii) `1/v - 1/u = 1 /f`
`1/v = 1/u + 1 /f`
`1/v = (f+u)/(uf)`
`⇒ v =(uf)/(f+u)`
= `((-24)(8))/((8)+(-24))`
= `(-24xx8)/(-16)`
= `(-192)/-16`
= 12 cm
(iii) m = `v/u = 12/-24 = -0.5`
The negative sign signifies an inverted image.
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