Physics 2000 Science Trek Electromagnetic Waves

Vibrating Charges and Electromagnetic Waves

Use your mouse to drag the negative charge up or down, then let it go to start it oscillating.
Use the slider to adjust spring tension.

This is cool. Wiggling one charge causes the field lines attached to it to wiggle, and after a time the other charge starts to wiggle! It's just like a rope connecting two rocks.
Yes, the wave here consists of a wiggling line of electric force which you can think of as being "attached" to the vibrating charge. Notice that it takes a certain time for the wave to move from one particle to the other. Check out what happens to the shape of the wave as you increase the frequency by wiggling it up and down faster. (The wiggling rate changes when you adjust the tension in the spring.) Does the distance between peaks (wavelength) decrease or increase?

Click here to learn more about the connection between wavelength, frequency and the speed of light.

Yeah, that all makes sense, but don't expect me to believe that particles as small as electrons are attached to springs. How is an electron made to wiggle -- I mean, how is its speed or direction of motion changed?

That's an excellent question. You're right, there are no springs -- so how do electrons wiggle? And do they always produce radiation when they wiggle? There are two answers, one for "long" wavelength radiation, like microwaves, radio waves and TV waves, and another answer for light waves, ultraviolet and x-rays. In fact, the second answer challenged the greatest physicists of the early 20th century, and led to the revolution in physics called quantum mechanics. Now you have to decide what kind of waves you want to see created.

For the advanced student: Learn more about wave shapes in order to understand microwaves, radio and TV waves, produced by oscillating currents.
Leaving Electromagnetic Radiation
Click "Quantum Atom" to learn how X-rays and light waves are produced by electrons moving in andnear atoms.