(a) State the relation between object distance, image distance and focal length of a spherical mirror.
(b) Draw a ray diagram to show the image formed by a concave mirror when an object is placed between pole and focus of the mirror.
(c ) A concave mirror of focal length 15 cm forms an image of an object kept at a distance of 10 cm from the mirror. Find the position, nature and size of the image formed by it.

Explanation

(a) `(1)/(v)+1/u = (1)/(f)`
(b) N/A
(c ) Here, `f =- 15cm, u= -10cm, v=?`
From `(1)/(v) + (1)/(u) = (1)/(f), (1)/(v) = (1)/(f) - (1)/(u) = (1)/(-15) + (1)/(10) = (-2+3)/(30) = (1)/(30)` or `v=30cm`
i.e, image is formed at `30 cm` from the mirror, As v is + , image is virtual and erect.
From `m= (-v)/(u) m = (-30)/(-10) =3`. Therefore, size of image is three times the size of object.