Question

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

Answer 1

We have to given that

F= -15 cm

If we place the object at infinity, then it will made the image at 'F' or 15cm,

So, we place the object in front of lens at any point before infinity.

Now,

F= -15cm , v= -10cm

=> u= ?

We know,

1/f= 1/v-1/u

So, we find that u= -30cm

Hence,

linear magnification i.e., m=?

We know, m= v/u

So, m=-10/-30

Hence, m=1/3.

Answer 2

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