Question

An object is placed at,12cm distance from the pole of concave mirror and the image formed at,4cm from the pole find the focal length of the mirror

Answer 1

Answer: f= 3cm

Explanation:

Answer 2

Focal length of the mirror is 6 cm and the image formed is real.

Explanation:

GIven:

  Object distance from pole 'u' = - 12 cm as object is left side of the mirror.

 Image distance from pole 'v' = 4 cm as image is real and on left side of the mirror.

Now, We know,

                          To find   Focal length 'f' for concave mirror.

Formual applied.

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

                             ⇒ $\frac{1}{f} = \frac{1}{4} - \frac{1}{12}$

                             ⇒ $\frac{1}{f} = \frac{2}{12}$

                           ⇒ f = 6 cm

 The image formed is real inverted as focal length is less than the object distance.

If the object is at right side of the focus of mirror, then image will be errect and virtual.