How far should an object be placed from a convex lens of focal length 20 cm to obtain its image at a distance of 30 cm from the lens? What will be the height of the image, if the objects is 6 cm tall?

Question

Philoid · Accepted Answer

According to the question;

Object distance = u;

Image distance (v) = 30cm;

Focal length = 20cm

By lens formula;

⇒ u = -60cm.

Therefore object is placed at 60 cm in front of lens.

Now;

Height of object h₁= 6cm;

Magnification = =

Putting values of v and u

Magnification =

⇒

Height of image is 3 cm.

Negative sign means image is real and inverted.