Jaguar,
Lurch gave you an incorrect answer, while Ultrapi1 is just venturing his own theory without having studied the subject. Only zapper gave you a correct answer. I think it is most productive to first read what very intelligent physicists have discovered during the last century and before. The first very successful description of light was by Maxwell, who considered ligth as a propagating oscillation in the electromagnetic field. Then we had a new and better description in the 20th century provided by quantum mechanics. Actually, Maxwell's description and the quantum-mechanical description are quite compatible. From a forum like this you can get a few opinions, but if you really want to understand this topic you will have to continue reading from books. If you don't like the very mathematical treatments, you can read some popularizations first.
Maxwell's equations describe light as electromagnetic radiation which consists of oscillations (waves) in the electric and magnetic fields which are always perpendicular to each other. This theory explains things like refraction, interference and polarization but does not tell you anything about photons.
Quantum mechanics describes light as emitted and absorbed in discrete bundles of energy called photons. Here the waves are interpreded more like probability waves (this is not exactly correct but an oversimplification). In a beam with a large number of photons, the probability translates into density of photons. This very rough description may give you the impression that these waves imply an ondulation in the density of photons along the beam. This is not so. The density usually remains constant (unless there is absorption). When the beam goes through two closely spaced slits, on the other side of the slits you do get regions of high and low photon density (light intensity). This phenomenom is called interference and is produced by the interplay between the two beams that went trough the slits.
The frequency of the oscillations in a beam of light is proportional to the energy in each photon, as demonstrated by the photoelectric effect, and in the case of light is related to the color of the light.
The intensity of the beam is proportional to the number of photons.
The polarization of light (that is explained by Maxwell) is related to the quantum-mechanical concept of spin. You can see the photon as a little top spinning around an axis that coincides with the direction of propagation. But while in clasical mechanics an object can spin only in one direcetion at a time, in quantum mechanics you have the paradoxical and counter-intuitive fact that an object can spin let's say clockwise and counterclockwise at the same time. Is like having two "realities" existing at the same time. It takes a while to get used to this new idea and to accept it. A photon spinning in one direction corresponds to a rotating electric field, and to what is called circular polarization. A photon that spins in both directions at the same time gives you, under the right circumstances, plane polarization, which means the electric field is oriented always in the same direction. You can find nice pictures in the books that show you the rotation of the vectors for circular and plane polarization. What they don't always make is the connection between the classical picture and the the quantum-mechanical concept of spin, which I understand was one of your concerns.
If I recall correctly, the text Optics by Hetch gives a good explanation of the connection between the classical and the quantum-mechanical pictures of light. I don't remember if the name was exactly "Optics" but you can do a search in Amazon.com with Hetch and Optics and you'll find it.
Good luck in your studies,
Oh! how do you measure a photon's frequency?
Prepare a beam of identical photons and , if they correspond to light from the ultraviolet to the near infrared (including the visible) pass it through a prism as in the typical experiment by Newton. Light of different frequency (wavelength) will be defflected by different angles. You can also use a grating instead of a prism.
--Alex--
