UPSC Civil Services Model Paper 4

Concave mirrors are used in vehicle headlights, searchlights, etc, to send parallel rays because it allows the light rays to be focused as a single beam and gives more power to the light, which makes it more efficient for seeing and to be seen by others.
If the mirror was not concave the light would be scattered which wastes energy and reduces efficiency. So, option 3 is correct.
For this, the source of light is placed at the focus of the concave reflector.
They are often used as shaving mirrors to see a larger image of the face. The dentists use concave mirrors to see large images of the teeth of patients.
Large concave mirrors are used to concentrate sunlight to produce heat in solar furnaces.