The formula governing reflection of light from a spherical mirror is
`(1)/(v) + (1)/(u) = (2)/(R )`, where
`u` = distance of object from pole of mirror,
`upsilon` = distance of image from pole of mirror
`f` = focal length of mirror,
`R` = radius of curvature of mirror.
This is known as mirror formula and is applicable equally to concave mirror and convex mirror.
`m = (I)/(O) = (upsilon)/(u)`
Read the above passage and answer the following questions :
(i) An object is held at a distance of `30 cm` in front of a concave mirror of radius of curvature `40 cm`. Calculate distance of the image from the object ? What is linear magnification of the mirror ?
(ii) The object is moved to a distance of `40 cm` in front of the mirror. How is focal length of mirror affected ?
(iii) What values of life do you learn from the mirror formula ?

Explanation

(i) When we change u, by moving the object, distance of image v changes. But focal length of mirror, i.e., f is not affected.
(ii) Here, `R=40cm`, `f=R/2 =40/2 = 20`cm.
(iii) In day to day life, an object is like a situation that comes up and image is like the response we give to it. We are like a mirror. Our nature/curvature determines our focal length. Response to a particular situation will depend upon our nature. One the contray, our nature/focal length is not affected by the situation that comes up.