A sensor is a device that detects and responds to some type of input from the physical environment. Sensors are used in everyday objects such as touch-sensitive door handles and light switches. They are also used in sophisticated applications such as industrial process control and robotic navigation. Sensors can detect a wide variety of physical phenomena, including temperature, pressure, humidity, motion, vibration, light, and sound. They can also detect chemical, biological, and nuclear changes. The output of a sensor is usually an electrical signal that can be used to control other devices or to provide data for further processing. Sensors are an essential part of modern technology, allowing us to interact with the physical world in a variety of ways. They are used in everything from medical devices to smart homes, and their use is only increasing as technology advances.