Question

if pencil beam is allowed to fall a long the principal axis of concave mirror the ray will​

Answer 1

The ray will deflect back along the principal axis only. As the pencil beam is small and it’s travelling along the principal axis it deflect back.

Answer 2

The ray will retrace the same path after relection.

Explanation:

• If pencil beam is allowed to fall along the principal axis of concave mirror, it strikes the mirror and reflection happens. The, it will retrace the same path after relection.
• Principal axis is defined as a line that is passing through center of curvature and the focus of a spherical mirror.

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Principal axis

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