The image formed by a spherical mirror is real, inverted and is of magnification - 2. If the image is at a distance of 30 cm from the mirror, where is the object placed ? Find the focal length of the mirror. List two characteristics of the image formed if the object is moved 10 cm towards the mirror.
CBSE OUTSIDE DELHI - SET 3 2016
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$m = -2$$\frac{v}{u} = 2$
$v = -30 \text{ cm}$
$u = -15$
$f \frac{uv}{u + v} = \frac{-15 \text{ cm }\times -30 \text{ cm}}{-15 \text{ cm + (-30) cm}} = \frac{450}{-45} = -10 \text{ cm}$
If the object is shifted 10 cm towards the mirror u = −5 cm
Therefore the object is between pole and focus and the image formed is:
$v = -30 \text{ cm}$
$u = -15$
$f \frac{uv}{u + v} = \frac{-15 \text{ cm }\times -30 \text{ cm}}{-15 \text{ cm + (-30) cm}} = \frac{450}{-45} = -10 \text{ cm}$
If the object is shifted 10 cm towards the mirror u = −5 cm
Therefore the object is between pole and focus and the image formed is:
- Virtual.
- Erect.
- Magnified.
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