Question

A concave mirror of focal length 10 cm is placed at a distance of 35 cm from a wall. How far from
the wall an object be placed so that its image formed by the mirror falls on the wall.​

Answer 1

Answer:

$\sf The\: object \: has \: to\: be\: placed \:at \:a\: distance\: of \:21 \:cm\: from\: the \:wall .$

Step-by-step explanation:

Here ,

Focal length(f) = -10 cm

Image distance(v) = - 35 cm

We have to find the value of object distance (u)

We know that by mirror formula ,

1/f = 1/v + 1/u

So,

-1/10 = -1/35+ 1/u

1/u = 1/10 - 1/35

LCM of 10 and 35 is 70

1/u = 7-2  

         70

      = 5/70 = 1/14 cm

Therefore , u = 14 cm

So the object has to be placed at a distance of (35-u)cm = (35 - 14) cm= 21 cm from the wall.