Watch the video to find out how an app can blow enough wind from your phone to blow out candles. A candle-blowing app can actually blow out a candle when you turn it on, but it’s not a real fan. Instead, it’s just a fake fan made to look like a real fan.
Sound waves cause the air to vibrate, creating areas of high pressure and areas of low pressure. But the individual air particles don’t move. Instead, they just vibrate back and forth in one place.
The sound generated by this app doesn’t just make the flame vibrate back and forth. Instead, it actually blows it in one direction.
The difference between sucking and blowing is that when the speaker membrane inside the iPhone moves outward, it expels air. Then when it moves inward, it sucks air back in, creating pressure waves.
In a shop vac, the side that blows air out pushes air into a column, and the side that sucks air in pulls air in from all directions. This is why blowing air out makes something coherent, and sucking air in does not.
The air coming out of the holes of the speaker is coherent when it is expelled, but when it is sucked in, it comes from all directions and does not have as much force to blow out the candle.
This app makes the sound like a fan is blowing air out of it, but it’s not really a fan in your iPhone.
Sound waves oscillate the air back and forth, creating a place of high pressure and then low pressure. So if you just look at a single air particle, you’ll notice it’s not moving anywhere.
If sound waves can’t move a mass of air, how can this app uses sound to blow out a candle?
Air constantly flows in and out of the tiny holes at the bottom of the iPhone. Still, there is a difference between sucking and blowing out.
When you blow air out, it’s like a column of air being pushed out of a vacuum cleaner. also, when you suck air in, it’s like a column of air being sucked in.
When the air comes out of the speaker, it’s coherent, but when it comes in, it’s coming from all directions, so it doesn’t have as much force to blow out the candle.