he inner surface of a cone coated by a reflecting layer forms a conical mirror. A thin incandescent filament is stretched in the cone along its axis aPhe minimum angle o of the cone for which the rays emitted by the filament will be reflected from the conical surface not more than once is greater than or equal to 120°. b) Ifangle ofcone is less than 120° the rays from the filament will be reflected from the conical surface not more than once c) Forany angle of cone multiple reflections of the rays from filament occurs d) lf angle ofcone is less than 120° the rays from the filament will be reflected from the conical surface more than once