An object 4 cm in height, is placed at 15 cm in front of a concave mirror of focal length 10 cm. At what distance from the mirror should a screen be placed to obtain a sharp image of the object. Calculate the height of the image.

Explanation

Here distance of object u = - 15 cm, height of object h = +4 cm and the focal length of concave mirror f = - 10 cm.
As per mirror formula `(1)/(v) + (1)/(u) = (1)/(f)`, we have
`(1)/(v) = (1)/(f) - (1)/(u) = (1)/((-10)) - (1)/((-15)) = - (1)/(30) rArr v = - 30` cm.
Thus, a screen be placed infront of mirror at a distance of 30 cm from it.
`because` magnification `m = (h.)/(h) = - (v)/(u)`
`therefore " "h. = - (v)/(u) xx h = - ((-30))/((-15)) xx 4 = - 8` cm
Thus, image is an inverted image of height 8 cm.