Concave mirror is used in headlights of vehicles, because it

Concave mirror is used in headlights of vehicles, because it

focuses light from the bulb onto nearby vehicles
sends parallel rays
fits well into the shape of the headlight
is cheaper than other mirrors
This question was previously asked in
UPSC NDA-2 – 2017
A concave mirror is used in vehicle headlights because, when the light source (bulb) is placed at or near its focal point, it reflects the light rays as a nearly parallel beam. This parallel beam effectively projects the light forward, illuminating the road ahead.
Concave mirrors are used as reflectors in headlights to create a focused, parallel beam of light by placing the light source at or near the mirror’s focal point.
Other options are incorrect: A concave mirror reflects light forward, not onto nearby vehicles in a focused way; while shape fitting and cost are practical considerations, they are not the primary *optical* reason for choosing a concave mirror. Parabolic reflectors, a specific type of concave mirror, are commonly used in headlights to produce a highly parallel beam.