Question

A spherical mirror produces an image of magnification -1 on a screen placed at 50 cm what is the focal lenght of the mirror

Answer 1

Answer:

The answer is -25cm

Explanation:

Answer 2

Answer:

As the magnification is -ve, we can say that the mirror is a Concave Mirror

Therefore,

m = -1

v = -50cm

u = ?

By Linear Magnification of Mirror,

$m=\frac{-u}{v}$

$-1=\frac{-u}{-50} \\u= -50 cm$

Now, by mirror Formulae,

$\frac{1}{f} =\frac{1}{v} + \frac{1}{u} \\\frac{x}{y} \frac{1}{f} = \frac{1}{-50} + \frac{1}{-50} \\\frac{1}{f} = \frac{1}{-50} - \frac{1}{50}\\\frac{1}{f} = \frac{-2}{50}\\\frac{1}{f} = \frac{-2}{50} \\\frac{1}{f} = \frac{-1}{25} \\Therfore,\\f= -25cm$

Explanation: