How Does a Smartwatch Know Your Heart Rate?

Smartwatches use light to measure your heartbeat. Inside the watch, there are tiny lights and sensors. When you wear it on your wrist, the light shines through your skin. Every time your heart beats, the blood in your arm moves, changing how much light is absorbed. The sensor sees that change and turns it into a number, your heart rate! It's like watching ripples in water to know how fast the boat is moving.

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Examples

  1. Imagine your smartwatch is like a flashlight shining on your wrist, it counts how much light bounces back to know when your heart beats.
  2. When you run, the watch keeps counting the waves of blood rushing through your arm.
  3. Your smartwatch turns heartbeat ripples into numbers, just like counting ocean waves.

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