Question

why does the incident ray reflect back on the same path in the concave mirror?

Answer 1

Answer:

because it is passing through center of curvature

Explanation:

where it is passed on normal

where angle of incidence and angle of reflection is equal to 0

this may help you

Answer 2

you learned that angle of incidence = angle of reflection

and angles are measured with the normal , right

for spherical mirror any line passing through the the centre of curvature becomes a normal, because its the centre of the sphere from which mirror is cut.

so any ray passing through centre of curvature has angle of incidence as 0° so it retraces its path to make angle of reflection 0°