Question

A ray directed towards the principal focus of a concave lens, after refraction, emerges:

Options

• Parallel to the principal axis

• Along the principal axis itself

• Through the optical centre with deviation

• Converging at the principal focus on the other side

Answer 1

A ray directed towards the principal focus of a concave lens emerges parallel to the principal axis after refraction. This is the reverse of the rule that a parallel ray appears to diverge from the principal focus on the same side.