__________ is used as reflectors in torchlight

Because when the bulb of torchlight is placed at focus of concave mirror, it allows the light to spread out to infinity (longer distances).

(b)this is incorrect because

convex mirror always forms virtual images so we can not put light bulb on virtual position so we can’t use convex mirror in torch light.

(c)this is incorrect because –

plane mirror can not spread light falling on it so we not use it in torch light.