Physics
Assertion (A) : A student is given a spherical mirror of focal length -10 cm. He identifies it as a concave mirror.
Reason (R) : Focal length of a concave mirror is always positive.
- both A and R are true and R is the correct explanation of A
- both A and R are true and R is not the correct explanation of A
- assertion is false but reason is true
- assertion is true but reason is false
Reflection of Light
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Answer
assertion is true but reason is false
Explanation
Assertion (A) is true because according to sign conventions (the mirror formula uses the Cartesian system), the focal length of a concave mirror is negative. So, a mirror with focal length –10 cm is indeed a concave mirror.
Reason (R) is false because the focal length of a concave mirror is always negative in mirror formula sign convention.
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