The figure shows an object AB at a distance u from the pole of a concave mirror. The image A[SUB]1[/SUB]B[SUB]1[/SUB] is formed at a distance v from the mirror. The position of the image is obtained by drawing a ray diagram.
Consider the D A[SUB]1[/SUB]CB[SUB]1[/SUB] and D ACB
[when two angles of D A[SUB]1[/SUB]CB[SUB]1[/SUB] and D ACB are equal then the third angle
But ED = AB
From equations (1) and (2
If D is very close to P then EF = PF
But PC = R, PB = u, PB[SUB]1[/SUB] = v, PF = f
By sign convention
PC = -R, PB = -u, PF = -f and PB[SUB]1[/SUB] = -v