An image is formed at a distance of 30 cm from a convex mirror when the object is placed 40 cm from the mirror. The magnification produced by the mirror will be _______.
+3/4
For a convex mirror, the image is always virtual and formed behind the mirror. Taking the sign convention where distances measured in the direction of incident light are negative: object distance \(u = -40\) cm, image distance \(v = +30\) cm (behind the mirror, same side as the reflected rays).
Magnification: \(m = -\dfrac{v}{u} = -\dfrac{+30}{-40} = +\dfrac{3}{4}\)
The positive sign confirms the image is erect (virtual); the magnitude less than 1 confirms it is diminished. The candidate chose −3/4 (option B), but a convex mirror always gives a positive (erect) magnification. The correct answer is : +3/4.
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