If m=1 in a concave mirror,
object will be placed at ć'.

f= -25cm
then u= 2 x -25= -50cm

Calculation of Object Distance in Concave Mirror
- Given:
- Magnification (m) = 1
- Focal length (f) = 25 cm
- Magnification (m) is defined as the ratio of the height of the image to the height of the object. In this case, m = 1, which means the image is the same size as the object.
- The formula for magnification in terms of object distance (u) and image distance (v) is:
- m = - v/u
- Since m = 1, we can rewrite the formula as:
- 1 = - v/u
- For a concave mirror, the focal length is negative. Therefore, f = -25 cm.
- The formula for the focal length of a concave mirror is:
- 1/f = 1/v + 1/u
- Substituting the given values, we get:
- 1/(-25) = 1/u + 1/u
- Solving for u, we find:
- u = -50 cm

Conclusion
- The object distance (u) in the case of a concave mirror with a magnification of 1 and a focal length of 25 cm is -50 cm. This means that the object is located 50 cm in front of the mirror.