Question

A mirror of focal length f is cut into two equal parts. what focal length of each part.
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Answer 1

Answer:

1.if it is a plane mirror,then both the parts will still have the same focal length (i.e infinity)

Answer 2

Answer:

There will be no change in focal length and hence focal length will remain the same.

Explanation:

• The point at which the reflected rays either really meet or appear to meet is the focal point of the spherical mirror.
• The distance between the mirror and the focus point (F) is known as the focal length (f).
• This is the distance away from the mirror where parallel light beams converged or diverged.
• The focal length is equal to half of the radius of curvature of the spherical mirror.

         F = ¹/₂ R.

• Since cutting the spherical mirror does not change the radius of curvature,  hence the focal length does not change.
• Therefore, the focal length of both parts will be the same.

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