A beam of light converges towards a point `O` ,behind a convex mirror of focal length `20` cm.Find the nature and position of image if the point `O` is-
(1) `10`cm behind the mirror, (2) `30`cm behind the mirror

Explanation

(a ) For this situtation object will be virtual as shown in figure .

Here u = + 10 cm and f= + 20 cm
`:. (1)/(v ) + (1)/(10) = (1)/(+20)`
i.e., v= 20 cm
i.e., the image will be at a distance of 20 cm in front of the mirror and will be real erect and enlarged with
`m= - [ -(20)/( 10) ] = + 2`
`(b )` For this situation also object will be virtual as shown in figure.
here u = + 30 cm and f=+ 20 cm ,br> `:. , (1)/( v) + (1)/(+30) = (1)/(20)`
i.e., v= + 60 cm
i.e., the image will be at a distance of 60 cm behind the mirror and will be virtual inverted and enlarged
with `m = - [ + (60)/( 30)] = 2`