Question

Can the above method be used for determining focal length of a) concave lens b) plano concave
lens?​

Answer 1

Answer:

no

Explanation:

because this is double convex lend

Answer 2

To determine the focal length of concave lens, we considered the distant objects.

• Let say the rays coming from far will fall on the concave lens, as the rays travel in parallel therefore they fall on the axis of the lens. Then image is formed near the mirror that is the principal axis.
• The image formed is inverted, real and small size.
• In the case of plano concave lens the focal length lies between 0-infinity.
• It can be negative.