# Create visible light with spinning magnet?

1. May 12, 2013

### jafeucht

Let's say you have a strong spherical neodymium magnet (for the purposes of this example, let's give it a 1 cm diameter), and you were to place it on a machine which rapidly rotates the magnet. If you were to rotate it at 100 MHz, could you build an FM radio transmitter? Supposing it were possible, if you were to increase the speed to 430 THz, will the magnet glow red? Has this experiment been done before?

What is the highest rotation frequency without causing damage to the magnet?

2. May 12, 2013

### Staff: Mentor

Back of the envelope says that the forces at the tips of a 1cm bar magnet spinning 100,000,000 times a second will be about 1012 that of the earth's gravity. That's far more than is needed to tear any macroscopic object apart.

(Don't take my word for it! You can check my math easily enough, the acceleration experienced by an object moving at speed v along a circular path of radius r is $\frac{v^2}{r}$)

Last edited: May 12, 2013
3. May 13, 2013

### lightarrow

And that's the reason why we prefer other ways to generate radio waves or light