List the sign conventions for reflection of light by spherical mirrors. Draw a diagram and apply these conventions in the determination of focal length of a spherical mirror which forms a three times magnified real image of an object placed 16 cm in front of it.

List the sign conventions for reflection of light by spherical mirrors

1.	List the sign conventions for reflection of light by spherical mirrors. Draw a diagram and apply these conventions in the determination of focal length of a spherical mirror which forms a three times magnified real image of an object placed 16 cm in front of it.
Answer» Solution :For new Cartesian sign convention for mirrors, see Point Number 15 under the heading "Chapter At A Glance". As per question and using the sign convention followed u = - 16 cm and magnification m = - 3 (because image is REAL). `therefore""m = - (v)/(u) = - (3) rArr v = 3u = 3 xx (-16) = - 48` cm `therefore""(1)/(f) = (1)/(v) + (1)/(u)` `= (1)/((-48)) + (1)/((-16)) = (1 + 3)/((-48)) = - (4)/(48) = - (1)/(12)` `rArr""f = - 12` cm The -ve sign of .f. shows that the MIRROR is a concave mirror. The ray diagram is shown in Figure.