Question

If parallel beams, non-parallel to principal axis fall on the convex lens, they converge at a point: (a) On principal axis (b) Away from principal axis (c) Centre of curvature (d) Called focus on the axis

Answer 1

if these parallel beams non parallel to principal axis fall on convex lens, one may pass through optic centre and pass without any deviation. another may pass through focus and after refraction passes parallel to principal axis. so they converge at a point away from principal axis.

Answer 2

If parallel beams, non-parallel to principal axis fall on the convex lens, they converge at a point: (a) On principal axis.

What is a converging lens?

• Convex lens is a converging lens which converges all incoming incident rays.
• Convex lens is a spherical refracting lens and is wider in middle and narrow at edges.

What is a principal axis?

• A principal axis is a straight line passing through the centre or pole of the lens.
• It is the straight line joining centre of curvature and pole of the lens.

What is focus?

• Focus is a point on the principal axis which is located at a distance half of the centre of curvature from the pole of the lens.

Parallel beams of light bends and converges to a point called focus on the principal axis.

Non-parallel beams of light converges at any point on the principal axis.