Answer to Question #130961 in Optics for Lucy

Question

A circular plate of radius 2cm is kept at a distance of 22cm in front of a concave mirror. The focal length of a mirror is 10cm. Calculate the perimeter of image formed if plate is kept coaxially to the principal axis. (Ans. 10/3π)

Answer 1

The real and inverted image created by a concave mirror is the same size as the object when both of them are located at the center of curvature of the mirror. at this point the object distance is equal to the radius of curvature of the mirror .

i.e

$U= radius\space of \space curvature\space of\space the\space mirror$

and $radius of curvature= focal\space legnth \times 2$

therefore$u=radies\space of\space curvature=15\times2 =30cm$

Answer$=30cm$