The negative value of the focal length of a spherical mirror indicates that it is:

Foundation

Physics Foundation

Reflection from spherical mirror

Question

concave mirror.

plane mirror.

convex mirror.

convex mirror of small focal length.

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The focal length (f) of a spherical mirror is related to its radius of curvature (R) by the formula: $f = \frac{R}{2}$ . By convention, the focal length is taken as negative for convex mirrors and positive for concave mirrors. A plane mirror has an infinite focal length. Therefore, a negative focal length specifically indicates a convex mirror, regardless of the magnitude of that length.

Final answer: convex mirror.