Question

For a concave mirror focal length is 9 cm and radius of curvature is 18cm

Answer 1

Answer:

YES but in magnitude

If we are assigning it direction also i.e. in sign convention.

The focal length would be -9 cm and radius of curvature would be -18 cm.

AND

2 × focal length ( f ) = radius of curvature ( r )

2f =r

I hope now your doubt is cleared.