A kid on a grassy hill holds up a little pocket radio and looks across at a tall radio tower, while golden radio-wave ripples arc through the open sky from the tower to the radio.

How does a song fly into your radio?

Nothing joins the tower to your radio — no wire, no string. Yet the music arrives. The secret: two clever tricks for hiding a sound inside an invisible wave.

First dial a wave has: how TALL it is. A taller wave carries a stronger radio signal. That is not the same as a higher musical note. Tap it.

tap the wave

Second dial: how SQUISHED the wiggles are. Closer wiggles mean more oscillations each second. They do not mean faster travel. Tap to compare.

tap the wave

To send a song, a radio bends just one dial in time with the music. AM bends the HEIGHT up and down. FM squishes the SPACING tighter and looser.

Two wave lanes: the top coral AM wave keeps even spacing but swells tall in the middle and shrinks again, while the bottom violet FM wave keeps one steady height but its wiggles squeeze close together then spread apart.

Your turn — be the station. Make a sound, and watch AM bend the height while FM bends the spacing.

the sound
AM radio
FM radio
the sound: singing
quietloud

Now a thunderstorm rolls in 🌩️

A slate storm cloud sprinkles short jagged crackle marks straight down onto two whole waves below it — a coral wave and a violet wave — both taking the very same falling crackle on their height.

It shakes the HEIGHT of every wave it touches. One radio hides its song in the height, the other in the spacing… which one survives? 🤔

You just saw: the storm shakes the height.

So whose music still sounds good — AM (hides it in the height) or FM (hides it in the spacing)?