Question

concave mirror, its real image is formed at
0.75 m from the mirror. Find the focal length
6. When an object is placed at 0.5 m from a
of the mirror and the magnification produced
by the mirror. (Ans. f = – 0.3 m, M= –1.5)​

Answer 1

Answer:

f = -0.3 , M = - 1.5

Explanation:

Given :

$v = - 0.75 = \frac{ - 75}{100} = - \frac{3}{4}$

$u = - 0.5 = \frac{ - 5}{10} = - \frac{1}{2}$

Mirror formula,

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

$\frac{1}{f} = \frac{1}{ \frac{ - 3}{4} } + \frac{1}{ - \frac{1}{2} }$

$\frac{1}{f} = - \frac{4}{3} - \frac{2}{1} = \frac{( - 4 \times 1) - (3 \times 2)}{3 \times 1} = \frac{ - 4 - 6}{3}$

$\frac{1}{f} = \frac{ - 10}{3}$

$f = \frac{ - 3}{10} = - 0.3$

Now, magnification

$magnification = - \frac{v}{u} = - \frac{ - \frac{ 3}{4} }{ - \frac{1}{2} } = - \frac{3 \times 2}{1 \times 4} = - \frac{3}{2}$

$Magnification = - 1.5$