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An object placed at the focus of a concave mirror produces an image:
AAt infinity, real and enlarged
BAt the focus point itself
CAt twice the focal length
DBehind the mirror as virtual
Answer & Solution
Correct answer: A. At infinity, real and enlarged
1. From the mirror formula with u = −f: 1/v + 1/(−f) = 1/(−f) ⇒ 1/v = 0 ⇒ v = ∞.
2. The image forms at INFINITY, highly enlarged and real.
3. This configuration is used in searchlights, where a bright source at the focus produces a parallel outgoing beam.
_Source: NCERT Class 10 Science Ch 9 Table 9.1 (image formation by concave mirror)_
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