Polarization

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Polarization

Introduction:

PART ONE: POLARIZATION

Method 1:

Two polarized disks were put into a grooved holder with their polarization axes lined up, and a bright red light emitting diode (LED) was placed on one side, and a light sensor was placed on the other side. Light intensity was measured as a function of the plastic rotating polarizer angle from 0 to 180 degrees. Science Workshop was used to measure the intensity for every 5-degree rotation (Fig 1).

Method 2:

The mineral calcite exhibits birefringence (double refraction), and therefore has two different values for its index of refraction. A calcite crystal was placed on top of print and rotated in order to see the difference between the two rays, the ordinary ray and the extraordinary ray. A polarizer was then used to look at the images formed by the calcite.

Method 3:

In order to determine the stress points in a plastic object, we used a photoelastic effect where we looked at the object through a polarizer. When the plastic was squeezed together, changes in the color occurred, displaying points with greater stress.

Method 4:

Polarization by reflection from a non-metallic surface was used in this method in order to help distinguish the plane of incidence, and Brewster's angle. A cardboard disk with a picture on it and a polarizer were placed in the holder, with a piece of black plastic (n=1.491) in between them. Brewster's angle was determined from tan = n, and =56. We then looked through the polarizer at this angle and were able to determine the polarization direction. We also viewed the reflection of a ceiling light directly above the black plastic in order to determine if it was polarized in this case.

Method 5:

In order to determine polarization by scattering, a jar was filled with water and dried milk, and then a flashlight was shined directly down into the top of the jar. From the side of the jar, we looked through a polarizer at the scattered light. From this we determined if the light was horizontally polarized.

PART TWO: LIGHT MEASUREMENTS

Method 1:

A halogen bulb light source was set up at the end of a yardstick, and a light sensor was set up on the yardstick beginning at 0.1m from the light source. Science Workshop was again used to measure the intensity of light ranging from 0.1m to 1.00m (Fig.

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