Question

show a simple calculation to verify that it is possible to obtain a real image as long as the object is outside the focal length of the concave mirror.

Answer 1

considering mirror formula

1/f = 1/di + 1/do

1/f - 1/do= 1/di

(do - f) / f * do = 1/di

di = f * do / ( do - f)

so for real image we need to maintain, do > f, i. e. we need to placed object outside the focal length in order to have real image

=====

Comment before rate in case any doubt, will reply for sure.. goodluck