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Ordinary light such as that from a light bulb is a form of wave motion that consists of electrical and magnetic fields that vibrate at right angles to the direction of travel of a light beam. Light waves that vibrate in a single plane are called polarized light waves. Such waves can be produced by passing light through polarizing filters. The experiment conducted was composed of crossed polarizers both qualitative and quantitative, polarization by reflection and of skylight were also tested by using a polarization filters. In conclusion, it was proven that polarization reduces unwanted reflected glare off surfaces.
If and only if a lens is polarized then regardless of orientation of incoming light waves light coming out of the polarized lens is always polarized in the direction of the polarization axis.
one flash light or desk lamp
two cable jumpers
one laser pointer
one multi meter digital
one capacitor set, PK, 4pcs, Capacitor LED, Diode, Photocell two clothespin
one polarizing cards (2)-PK
First one polarizing filter was placed on top of the other so that light is transmitted. Then with two filters were put together and aligned so that light passed through them, looking through them at a bright light in this case a flash light was used. Then slowly one of the filters was rotated through 360o while keeping the other one still. Observations were then recorded.
From my observation in part one by placing the two filters together one in front of the other and slowly rotating one of the filters I notice that light between them became brighter as one filter was being rotated then the light became a dark blue shade.
In part two of the experiment one polarizing filter was placed on top of the other so that light was transmitted. Next cloth pins were attached to each side of the bottom edge of the combined filters. The clothes pins supported and allowed the filters to rest perpendicular to a table where they were placed. A CDS cell was then placed behind the filter assembly so that the photocell’s light sensitive surface was unobstructed and faced to the Polaroid filter assembly about 5 to 10 cm away from the center of the filters. To support the photocell it was taped to a drinking glass. The illustration below shows the basic configuration you need to achieve. Next the two wires of the photocell were attached to the DMM via two jumper cables.
The DMM was set as an ohmmeter. The resistance had to be inversely proportional to the incident light intensity. Then using a flash light that and paper cone to focus the light, shine light through the polarizing filter assembly at the photocell. Because the filters were aligned to allow light through, the angle between them was zero. The angle and the corresponding resistance was then recorded. The last step in this experiment was to rotate one of the filters 15o and take another angle and resistance reading; while doing this the positions of the light source and photocell couldn’t change thorough out the experiment. Additional readings were taken every 15o though a complete 360o of the rotating filter. Finally the outcomes of each light intensity reading was graphed using 1/R vs. angle between polarization axes.
As I tried to shine the light through the filters as one was being adjusted to the angle given, I noticed that as the angle increased it was more difficult for the light to shine through. My observation when measuring the resistance are recorded above. The digital multi meter was set on 200 ohms.
In part three “Polarization by Reflection” looking out the window at a car windshield that is reflecting sun light. Then holding each of the two linear polarizing filters in front of the eyes in a way that best reduces the glare from the window. Then a vertical mark was made on top of the filter while it is in this position. The lines made marked the transmission axis of the filters. Next noticing how the best glare reduction is achieved from a filter with its transmission axis in a vertical position the light reflected from a horizontal surface is horizontally polarized. This experiment illustrated the way polarized sunglasses reduce glare from snow, ice, water and the front of your car.
When working with this part of the experiment I noticed that I was indeed less bothered from the glare when I held one of the filter that had its axis in a vertical position.
PART IV –
In part five of this experiment polarizing filters were used to look at the sky at 90 degrees to the direction of the sun. Looking at different regions of the sky and noticing if the intensity of the light changed as you rotate the polarizer.
When holding the polarizing filters in a bright region of the sky, I noticed that the region I was looking at became dark as I was rotating one of the polarizing filters.
1. If you buy sunglasses how can you be sure they are truly polarized? When buying polarized sunglasses you can make sure they are truly polarized by holding two pairs of identical sun glasses together one in front of the other in such a way that you are able to see through them; then slowly rotate one of the glasses to about a 90o angle, and if your vision through the second lenses gets visibly darker that means they are indeed polarized sunglasses.
In conclusion polarized lenses helps to reduce unwanted reflected glare off surfaces such as those from the water, road, and even snow covered areas.
Throughout the experiment using the polarized filters it was clear that when rotating one the filters the image or region being looked at increased in brightness and then it became dark making it difficult to see through the filters. This was proven multiple times when looking at bright regions of the sky, and looking out the window of a car windshield that was reflecting sunlight. Problems were encountered when conducting part two of the experiment, it was difficult to position the polarizing filter at the precise angles. As the angle increased the light beam did not shine through as much as it did in the angles less the 90 degrees.