Why are paraboloidal mirrors used in car headlights and searchlights instead of using spherical concave mirrors?

Explanation

Parallel rays of high intensity even at a large distance are required for motor car headlights and search-lights.
We know that if a source of light is placed at the focus of a cave mirror only paraxial rays travel parallely ahead after reflection in the mirror. But the other rays do not travel parallely. the rays spread after traversing only a little distance and intensity at a large distance becomes very low.
But, if a source of light is placed at the focus of a paraboloidal mirror, all the reflected rays advances parallel to the principal axis. So, the intensity remains high even at a large distance. this reason, paraboloidal mirrors are used in car headlights and searchlights insetead of spherical concave mirrors.