[b][i]Spherical Mirrors Vs. Parabolic Mirrors[/i][/b] Reflexion on a Spherical Surface Spherical Mirrors: Concave mirror, Linear object ★Parabola plotted with equal focus f = (2.0) as the approximate spherical mirror. ★The parabole does not generate the error FOCUS. ★The spherical mirror fails for angles that deviate from its approximate coincidence with the parabola.