The correct answer is option 2. A concave mirror is used in the headlights of vehicles because it sends parallel rays.
To understand why this is the case, we need to understand the properties of a concave mirror. A concave mirror is curved inward, meaning it has a shape similar to the inside of a bowl. When light rays pass through this mirror, they are reflected inward and converge at a specific point, called the focal point.
In the case of vehicle headlights, the light bulb is placed at the focal point of the concave mirror. This arrangement allows the mirror to focus the light rays that are emitted from the bulb and reflect them in a parallel manner.
By sending parallel rays, the concave mirror ensures that the headlights illuminate a larger area in front of the vehicle. This is important for safety reasons, as it improves visibility for the driver and helps to prevent accidents.
Therefore, option 2 is the correct answer because a concave mirror is used in headlights to send parallel rays of light.