What is the focal length of a convex lens of focal length 30cm in contact with a concave lens of focal length 20cm? Is the system a converging or a diverging lens? Ignore the thickness of the lenses.
Focal length of convex lenses, f1=30cm Focal length of concave lenses, f2=−20cm ⇒f1=f11+f21 f=−60cm. Therefore diverging lens .
