Hi JD,
Doubtless, a real-live physicist could explain things better than I, but I'll do my best.
Light indeed consists of an electromagnetic wave with two components -- an electrical field and a magnetic field at right angles to each other. The photon is said to be the "carrier" of the electromagnetic force, as its motion generates the wave.
At the level of individual photons, there's no clear distinction between the wave-like properties and the particle-like properties of the photon. Still, for practical purposes, the moving photon (but then, photons are
always in motion, more or less by definition) generates the fields. Or maybe the moving fields generate the photon. After all, light is both an electromagnetic wave
and a photon. Whether it behaves more like a wave or more like a particle depends upon what you're trying to measure. (Somebody once said that if you think you understand quantum physics, you're wrong.)
Here's a neat little java
applet that shows how the electrical and magnetic fields oscillate at right angles to each other and to the direction of motion.
All electromagnetic waves are "light." It's just the case that we can see only a tiny portion of the electromagnetic spectrum. The less energy a photon has, the slower its "vibration," and so the longer is its wavelength (and, consequently, the lower its frequency).
Photons with the least energy have wavelengths measured in
kilometers for the very lowest energy levels, up to wavelengths of about a meter for relatively high energy levels. This portion of the electromagnetic spectrum is what we call "radio" waves. It's simply low-energy light.
"Microwaves" are somewhat more energetic, and so have wavelengths in the centimeter to millimeter range.
"Infrared" radiation is more energetic still, but not as energetic as visible light.
"Visible light" is that very narrow band of the electromagnetic spectrum to which our eyes happen to be sensitive. It ranges from least energetic (red) to most energetic (violet).
More energetic than violet light is "ultraviolet."
Beyond ultraviolet light are "x-rays," and finally, the highest-energy (and thus shortest wavelength) light waves are "gamma rays."
High-energy light is dangerous precisely because it has so much energy. This makes it quite good at penetrating into matter. Ultraviolet radiation can penetrate into the skin, where it damages DNA molecules, sometimes causing skin cancer in the process. Higher-energy x-rays can go right through flesh, but are stopped by denser bone. Since they penetrate deeper into the body than does ultraviolet radiation, x-rays can cause damage to cells deeper in the body.
Gamma rays have such small wavelengths that to them, the human body is mostly empty space. That's fortunate in a way, because they can pass right through your body without hitting anything in the process. So, an individual gamma-ray photon is actually
less likely to cause damage than is an x-ray photon. On the other hand, gamma rays are
so energetic that they can damage individual
atoms, should they impact them. This means that any gamma photon that happens to be absorbed by body tissues will do quite a bit of damage in the process.
Cheers,
Michael