Question

A concave lens has focal length of 15cm. At what distance should the object from the lens be placed so that it forms an image at 10cm from the lens? Also find the magnification produced by the lens.

Answer 1

Given :- h = 2 cm , f = - 15 cm , v = - 10 cm .

To find :- u = ? , nature = ? , h' = ?

Solution :-

For lens :-

1 / v - 1 / u = 1 / f

1 / v - 1 / f = 1 / u

1 / - 10 - 1 / - 15 = 1 / u

1 / u = - 1 / 10 + 1 / 15

1 / u = - 3 + 2 / 30

1 / u = - 1 / 30

u = - 30 cm

m = h' / h = v / u -------- ( for lens )

h' / 2 = - 10 / - 30

- 30 h' = - 20

h' = 2 / 3 = 0.6 cm

Nature :- Image formed is virtual , erect and diminished .
Size :- Size of image is 0.6 cm

Answer 2

Explanation:

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