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IS LIGHT A WAVE
Finally, we get to the reason we're talking about waves in the first place. Is light a steady stream, or does a wave action go on there too? Some believed a beam of light was continual. Others, like Newton, thought light traveled in teeny bits. Can we decide?
A steel tuning fork vibrates at some standard rate, perhaps four hundred forty times per second. Piano tuners use the fork to get started with that first string. In a college physics class, we had a device by which we could see sound waves, or at least it showed the vibrations of the steel (a tuning fork) used to generate sound waves.
A needle, attached to the fork, just barely touched a four-foot, smoked-glass panel. The vibrating tuning fork dropped down the slide, and the needle scratched a line in the smoky glass. The crests spread as the fork accelerated because of the force of gravity. We saw the separate waves at the bottom of the glass.
What about light? If we drop a light down the slide, can we perhaps see the light start to flicker? No, and you'll find out why later.
But someone did come up with a way to test for light waves. Remember how the waves in the water messed with each other creating secondary waves? The waves in the air also interfered with each other creating a beat-frequency, a secondary wave slow enough to hear.
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