28. An object of size 7em is placed at 27em in front of a concave mirror of focal lengthi Scm. Where is the sharp image formed? Find the size and nature of the image. Alsofind the magnification

28. An object of size 7em is placed at 27em in front of a concave mirr

1.	28. An object of size 7em is placed at 27em in front of a concave mirror of focal lengthi Scm. Where is the sharp image formed? Find the size and nature of the image. Alsofind the magnification
Answer» <p>We know that, for a concave mirror the focal length will be negative.Therefore,given: u = -27cm f = -18cm h(object size) = 7cm</p><p>( Note that the distance at which you will obtain sharp image will be your "v" i.e. the object distance for that image formation which is required in the question)</p><p>hence,1/v + 1/u = 1/f(mirror formula)1/v + (1/(-27)) = 1/(-18)1/v = 1/27 + 1/-18 ( LCM of 18 and 27 is 54)1/v = 1/(-54)v = -54cmimage distance = -54cmhence, image is formed on the same side.</p><p>now we know,h'/h = -v/u(h' denotes object height)h'/7 = -(-54)/-(27)h' = 7 * (-2)h' = -14cm</p><p>hence, image is inverted (since h' is negative) and it is on the same side of that of the object (since v is negative).</p>