A concave mirror forms a real image 4 times the object height. If the distance between object and image is 45 cm, find |f| in centimetres.
Physics · Geometrical optics · spherical mirror
JEE Mains NEET

Question

A concave mirror forms a real image 4 times the object height. If the distance between object and image is 45 cm, find |f| in centimetres.

G1 Physics · Accepted Answer

v=4u and v−u=3u=45, so u=15 and v=60. Therefore f=uv/(u+v)=900/75=12 cm.