You step up to the sink. The water starts to flow. You don’t have to touch a thing!

What makes some faucets turn on and off on their own? If you look closely, you might find the sensor on the bottom of the faucet. This area sends out infrared light. You can’t see infrared light. But the infrared light lets the faucet “see” you.

Here’s what happens. The faucet is always sending out rays of infrared light. You put your hands under the faucet. The infrared light bounces off your hands and back to the sensor. This causes the faucet to turn on. You wash your hands. Then you reach for a paper towel. Your hands move away from the faucet. The infrared light no longer bounces back to the sensor. So the water turns off.

Why do people use such fancy faucets? The answer is simple. They save water. Sometimes people forget to turn the water off after they wash. Infrared faucets turn themselves off.