A small candle 2.5 cm in size is placed at 27 cm in front of a concave mirror of radius of corvature 36 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Describe the nature and size of the image. If the candle is moved closer to the mirror, how would the screen have to be moved ?

Explanation

u = - 27 cm, f = - 18 cm
`(1)/(v) + (1)/(u) = (1)/(f), " " (1)/(-27) + (1)/(v) = (1)/(-18) " " therefore v = (-18 xx 27)/(27 - 18) = - 54` cm
`m = (h_(i))/(h_(0)) = (-v)/(u), (h_(i))/(2.5) = (-(-54))/((-27)) = - 2`
`h_(i) = - 5 ` cm `" " therefore` The image is real, inverted and magnified.