An object 4 cm in size is placed at a distance of 25 cm from a concave mirror of focal length 15
cm. Find the position, nature and height of the image.

Dear Student

Given
f = -15 cm;
u = -25 cm ;
hi = 4 cm;
v = ?

According to the mirror formula,
1/f = 1/u + 1/v

1/-15 = 1/-25 + 1/v
1/v = 1/25 - 1/15
1/v = 3 - 5/ 75 
v =-37.5 cm

Hence, screen should be placed 37.5 cm from the pole of mirror and the image is real.
Magnification, m = hi / ho = -v/u

hi / 4 = 37.5 / 25

hi = 37.5 / 25 x 4 = -6 cm

The image formed is real, enlarged and inverted.

Regards

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