article_snippet: On the back of the Apple Watch's case is a sensor (pictured) that uses infrared and visible-light LEDs and photodiodes to detect the wearer's heart rate .
article_snippet: Vibration and notifications: the Apple Watch has a built-in is a 'taptic engine' that responds to a subtle vibrations users feel on users wrist for notifications.
article_snippet: This is made from a linear actuator, or motor, inside the Apple Watch that produces haptic feedback.
article_snippet: On the back of the Watch's case, a ceramic cover with sapphire lenses sits above a sensor that uses infrared and visible-light LEDs and photodiodes to detect the wearer's heart rate.
article_snippet: Apple Watch uses a sensor that uses infrared and visible-light LEDs and photodiodes to detect the wearer's heart rate, along with an accelerometer and the GPS and Wi‑Fi in a connected iPhone, to measure physical movement such as steps, distance and calories.