Experiments with light?

Question

I am wondering if a magnetic field will effect light?
If it does, can you suggest an experiment I can do at home to illustrate this.
Thank you in advance.

Answer 1

There are two effects of a magnetic field on light. The Faraday effect occurs when polarized light is passed through certain materials, such as carbon tetrachloride, in the presense of an axial magnetic field. The magnetic field causes the plane of polarization of the light to rotate with respect to its axis of propagation (and the axis of the magnetic field).

This is fairly easy to demonstrate at home with crossed polarizing films (obtain from Edmund Scientific) and a bright light source. You also need a container for the carbon tetrachloride that will allow the light to pass through it and an electromagnetic coil wound around the container in the direction of the light propagation. A foot long piece of glass tubing with glass plates glued to each end will work. Cut the top and bottom off a straight-sided wine bottle.

Wind a few hundred turns of 16 AWG insulated copper wire around the glass tube and tape it in place with black electrical tape. Neatness does NOT count. Just scramble wind it like you would a kite string on a stick.

Using a silicone RTV cement, cement a glass plate to one end of the glass tube. Allow this to cure at least 24 hours. Fill the glass tube with carbon tetrachloride and cement the other end in place. Allow the RTV cement on this other end to cure for at least 24 hours also. Or, you can get fancy and add a filler hole and plug in the side of the glass tube.

Place one polarizer over one end of the glass tube and the other polarizer over the other end. The light passes through the first polarizer, the container of carbon tetrachloride and lastly through the second polarizer. Turn on the light and adjust one of the polarizers to dim the light passing through the carbon tetrachloride as much as possible.

Now pass a current through the coil (you may need several amperes, depending on how many turns you wound the coil with; more turns is better) and observe that the light passing through the second polarizer brightens.

Congratulations, you have just demonstrated the Faraday Effect.

The other magnetic field effect on light is called Zeeman Splitting. It is a quantum mechancal effect that causes a slight shift in the wavelength of light emitted from an excited electron when it drops back into a lower state. Depending on whether the electron spin is aligned with or against the magnetic field, the photon energy will be increased or decreased compared to no magnetic field. This is also fairly easy to accomplish by placing a helium-neon laser tube inside a solenoid electromagnet, but observing the effect is difficult because there is only a few megahertz shift in the light frequency, depending on the strength of the magnetic field. The Zeeman effect was used by Hewlett-Packard to construct an interferometer for measuring distances very accurately, typically on the ways of precision machine tools.

Answer 2

An external magnetic field will not affect light, even though light consists of variations in electric and magnetic fields. The magnetic field variations in light are just "superimposed" on the external field in a linear manner.

Answer 3

not at home unless you have an extra black hole or can get a shot of it bending. Fascinating ain't it. Light is affected by gravity.