Question

The point on the principal axis of a convex lens, such that rays of light starting from it on passing through the lens, move parallel to the principal axis is called ______.

Options

• first focal point

• second focal point

• optical centre

• aperture of lens

Answer 1

The point on the principal axis of a convex lens, such that rays of light starting from it on passing through the lens, move parallel to the principal axis is called first focal point.

Explanation:

Rays starting from the first focal point of a convex lens emerge parallel to the principal axis. The second focal point is where parallel rays meet; the optical centre and aperture are not focal points.