Calculate the magnification of convex lens of focal length 10 cm when the image formed by lens is erect at the distance of nearest point of vision.

Given

Focal length of convex lens = + 10cm (focal length of convex lens is always positive)

Since nearest distance of vision is 25cm

Formula Used

Lens Formula

Magnification formula

Now let’s re-write the above formula

Using mirror equation

Now replacing the ‘u’ in magnification equation with the above u we get

Now, according to our sign convention v is negative and equal to D (nearest distance of vision)

Hence the equation becomes

Putting the values, we get

M = 3.5