Question

)
An object when placed at a distance of 25 cms from a correr
lens produces a double sized real images the other
the lens. Calculate -
The image distance

The focal length of the lens.​

Answer 1

Given

-------

u=-25 cm

magnification= - 2

To find

-----------

v=?

f=?

Solution

-------------

By lens formula,

1/v-1/u=1/f

_______(1)

And by magnification formula of lens,

m= v/u

-2=v/-25

v=+ 50 cm

Now, putting the values of v and u in (1)

1/50-1/-25=1/f

=>1/50+1/25=1/f

=>3/50=1/f

=>f=50/3 cm

Answer

-----------

Hence, the value of image distance is +50 cm and the value of focal length is +50/3cm.