Background Information:

The process of polarizing light is known as polarization. In the experiments performed in this laboratory, light is polarized using both a polarized laser and several different polarizing filters. A polarizing filter is able to filter out half of the vibrations that pass through the filter. Only light waves that flow parallel to the electric field of the polarizer actually becomes transmitted through. Light that flows perpendicular to the electric field is absorbed and blocked from exiting through to the other side.

My Experiment:

Part I: Polarization of light through an extremely small amount of milk and water.

This picture is the setup of our investigation. Here, I am setting up the laser to point through a beaker with an extremely small amount of milk in water. The mount of milk we used in the first part of the experiment was so small, that I only used about five drops of milk.

Most of the pictures taken during this experiment were taken in the dark, so we could get the full effect of the laser through the water. These two pictures were taken with a polarizing laser and the small amount of milk. As you can see from the side and top view of the beaker, the laser is fully visible through the beaker. The other interesting thing that was observed during this experiment was that when the electrical field is in a certain position, light can only be seen through either the top or the side of the beaker!

Electrical Field         Up and Down                Side to Side
       Top            Dark (No Visible Light)	  Bright (Visible Light)
       Side           Bright (Visible Light)      Dark (No Visible Light)

As electrons are bouncing up and down in the wave, the light is not visible from the top view, where as the laser is at its brightest when seen from the side view in this position. This was really interesting to see the differences between the top and side views at the same time.

When a second polarizer is put into the equation, the effects become even more interesting. If the second polarizing instrument has its electrical field perpendicular to that of the first polarizer, the light that becomes transmitted is blocked by the additional polarizer. The first two pictures above show the effects of an additional polarizer which is perpendicular to the electrical field of the polarizing laser. Here the electrical field of the polarizing laser is up and down while the electrical field of the additional polarizer is side to side. The third picture in this trio is a picture with both polarizing devices in the same directional field.

Although the pictures for this portion of our observations did not come out extremely clear, I will briefly explain them anyway. The first picture was supposed to be the laser with the electrical field side to side and the second polarizer perpendicular to this. No light is visible through this polarizer. The second picture which is only semi-visible is the polarizer and the laser parallel to one another. Here light should be able to shine through and be visible through the polarizer.

Part II: The Addition of Milk to Water Solution and its Effects on Polarization.

These are the pictures from the setup of the second part of the experiment. Here we can see the laser fully shining through the clear water before any milk is added in a fish tank. Both in the light room and dark room it is visible clearly through the front view.

Both pictures were taken when there was 1ml of milk added to the water. It is extremely interesting to see the two different effects of the dark and light. The light picture looks like cloudy water and a beam of light, while in the dark there are only a few dots of light in a row, where the beam should be. This is really fascinating! The final picture is a top view while the light is on in the room; here the laser is barely visible, only truly visible right near the entrance of the laser.

As the level of milk increases the effects this has on the polarizer are very interesting. Here are three pictures of water with a total of 5ml of milk added to it. From the first view, which is looking directly at the laser, barely light is visible. The second view is from the top, which looks like a progression of the previous view of the top, with only a slight view of the laser. In the dark it is clear that the light is not only moving in one direction, but it is dispersing outward like a fan.

Another interesting thing can be seen from the above pictures. All three pictures are taken from the top view of the 5ml addition of milk. Although it seems from the appearance of the light in the tank that the light is becoming depolarized, which it is, this has not fully taken place yet. This is evident by the first and second pictures above. The first picture was taken with a second polarizer perpendicular to that of the laser. The light is definitely still polarized, because otherwise there would be no change in light coming though the second polarizer. The second picture has the polarizer parallel to the laser and here, the light is completely visible through the polarizer. There is something very special about the third picture above. In the third picture the polarizer is 20� clockwise from the transverse position. As observations were being made during this portion of the experiment, we could notice that the shadow of light that was moving as we turned the polarizer was moving along with the rotation of the polarizer. Here the top portion of the laser is visible but the bottom portion is still in darkness. The same thing occurred when we turned the polarizer counter clockwise. Here the top of the laser is in darkness while the bottom portion is bright. This again was another wild observation!

As the amount of milk increases, the effect of the polarizer become less and less. Here the first picture has the polarizer transverse to the laser, while the second picture has the polarizer parallel to the polarizer. As the concentration of milk increases, less and less of the original beam can be seen.

At 15ml of milk, the frontal view of the laser is completely diffuse. Here the completely scatters out from the middle. Also there is barely any polarization left on the light in the water. Both of the pictures above look identical, with the polarizer in two different positions.

The final dilution of milk was done with 50ml. The first picture is very interesting, half of the tank is bright, and the other half is dark. The second picture is a back view of the laser, showing the light dispersing from the one solitary dot. The final two pictures here show no change between the polarizer and its different positions, showing that the light is completely unpolarized!

This final picture shows a beaker with 100% milk and the polarized laser. Here there is one solitary section of light that stops abruptly.

Discussion:

Special Thanks:

Links:

Examples of Scattering Light This is another website that gives a brief overview of scattering light. In addition to this, the website also has a similar experiment to the one that I did in this lab.

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