The image formed by a concave mirror of focal | vedclass

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(A) For a concave mirror,the focal length $f = -6 \ cm$. The magnification $m = \pm 3$.Using the formula $m = \frac{f}{f-u}$:Case $1$: For a real imag

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$-4$

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(A) For a concave mirror,the focal length $f = -6 \ cm$. The magnification $m = \pm 3$.Using the formula $m = \frac{f}{f-u}$:Case $1$: For a real image,$m = -3$.$-3 = \frac{-6}{-6-u}$ $\Rightarrow -3(-6-u) = -6$ $\Rightarrow 18 + 3u = -6$ $\Rightarrow 3u = -24$ $\Rightarrow u = -8 \ cm$.Case $2$: For a virtual image,$m = +3$.$3 = \frac{-6}{-6-u}$ $\Rightarrow 3(-6-u) = -6$ $\Rightarrow -18 - 3u = -6$ $\Rightarrow -3u = 12$ $\Rightarrow u = -4 \ cm$.Thus,the possible distances of the object from the mirror are $4 \ cm$ or $8 \ cm$. Given the options,$-4$ is a valid coordinate representation.

The image formed by a concave mirror of focal length $6 \ cm$ is $3$ times the size of the object. The distance of the object from the mirror is......$cm$.

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