Question

An object is placed in front of a concave mirror of focal length 18 cm ..If a real image is formed at 54 cm find the object distance.

Answer 1

Answer:

f= -18 cm v= -54 cm

Using mirror formula :-

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

$- \frac{1}{18} = - \frac{1}{54} + \frac{1}{u}$

$- \frac{1}{18} + \frac{1}{54} = \frac{1}{u}$

$- \frac{3}{54} + \frac{1}{54} = \frac{1}{u}$

$- \frac{2}{54} = \frac{1}{u}$

$u = - \frac{54}{2}$

$u = - 27cm$