Question

A ray passing through the principal focus of a convex lens, after refraction, emerges:

Options

• Parallel to the principal axis

• Through the optical centre undeviated

• Through the principal focus on the other side

• Diverging from the same focus

Answer 1

A ray passing through the principal focus of a convex lens emerges parallel to the principal axis after refraction. This is the reverse of the rule that a ray parallel to the axis converges at the principal focus, consistent with the reversibility of light paths.