Question

if the magnification of a mirror is - 2 and its focal length is 15 cm what is the object distance​

Answer 1

Given:-

• magnification of a mirror= -2
• Focal length=15cm

To Find:-

• distance of the object.

Solution:-

we know that

$\sf\huge \: m = - 2 = \frac{v}{u}$

so,

$v = - 2u$

For finding the distance we use lens formula

i.e,

$\huge\frac{1}{u} + \frac{1}{v} = \frac{1}{f}$

now, substituting the value in this equation

$\frac{1}{ - 2u} + \frac{1}{u} = \frac{1}{15}$

$= > \frac{1}{15} = \frac{1}{u} - \frac{1}{2u}$

$= > \frac{1}{15} = \frac{2 - 1}{2u}$

$= > \frac{1}{15} \times 2u = 1$

$= > u = \frac{15}{2}$

$= > u = 7.5cm$

∴the object distance is 7.5cm

Answer 2

Explanation:

answer is 7.5 m

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