Question

An object is held at a distance of 20cm from a concave lens of focal length 80cm. What is the

Answer 1

Answer

it is -16

explanation

Here, u=−20cm,f=−80cm,v=?,h1=2cm,h2=?

From 1v−1u=1f,1v=1f+1u=1−80−120=−1−480=−580

v=−805=−16cm.

Thus, image is at 16 cm from the lens on the same side as the object.

As h2h1=vu∴h2=vuh1=−16−20×2cm=1.6cm

This is the size of the image.