Question

An object is placed at a distance of 20 cm from a concave mirror . The image is doubled the size of the object and is inverted . Find the focal lenght of the mirror and the position where the image is formed.......


( HINT : ANSWER IS 16 CM .. 48 CM ) ​

Answer 1

Answer:

u= -20 cm,v=?

let object's size be x cm,

then, image's size be -2x.

Now, magnification= hi/ho

= -2x/x

= -2

Again, magnification= -v/u

-v/-30=-2

v= -60cm.

Now, by mirror formula,

1/v+1/u=1/f

-1/60+(-1)/30=1/f

this implies, f = -20cm