A proximity sensor is a device that detects the presence of nearby objects without any physical contact. It works by using various technologies, such as infrared light or electromagnetic fields, to sense when something is close. Commonly found in smartphones, these sensors help to turn off the screen during calls when the phone is held to the ear, preventing accidental touches. These sensors are also widely used in other applications, like automatic doors and security systems. For example, in a smart home, a proximity sensor can trigger lights to turn on when someone enters a room, enhancing convenience and energy efficiency.