By Anupum Pant
We’ve all seen automatic faucets and this is how they work. You put your hand, the water flows and stops automatically when the hand moves away. Or that is how they are supposed to work.
I came to US about 1 year back. Since then I’ve been to a number of restrooms which have automatic faucets in the sink. But every time I try to use them, these things fail me. I used to think it was due to the darker color of my skin, but then that was a little too far-fetched. I was pretty sure it was me who was doing something wrong in the foreign country. Probably things worked a little different here because we had the same things back in India too, they worked pretty well with my brown skin color.
And then I stumbled on this viral video which demonstrated the same thing. My first guess seems to be right. To confirm that I dug a little deeper.
This redditor seems to know why this happens. The sinks work because they shoot off an infrared beam outwards. When this beam is unobstructed, it is programmed to not send out water, or soap, like in this case. When these get obstructed by something that is close, the body reflects back some of the infrared back. That is how the faucet knows something is close.
Darker bodies however are known to be better absorbers. So, they absorb most of the infrared and send only a tiny amount of it back which is apparently not enough to trigger the faucet. The amount of reflected signal it receives before it can be triggered apparently can be tuned by doing trials. Probably since faucet companies in the US use white people for trials, they have a default trigger which requires a greater amount of reflected light, on an average. So it works for white skinned people but seems to fail people with darker color.
However, in India since these tests must be done with people who mostly have a slightly darker skin color, the faucets are probably programmed to work fine with that kind of skin color and for white skins too.