Experiment 4 - General Physics Laboratory II | PHYS 1102, Exams of Physics

Download Experiment 4 - General Physics Laboratory II | PHYS 1102 and more Exams Physics in PDF only on Docsity! PHYS 1102 Polarized Light Experiment 4 PROCEDURE EXP 4 1. Position the Translator with the Optical Fiber on the rail so that the end of the fiber is aligned with the 100 mm mark on the scale. Position the Light Source on the rail so that the filament of the bulb is aligned with the 600 mm mark on the scale. Place the 48 mm focal length lens on the side of the carrier facing the optical fiber and at a distance of 48 mm from the fiber. Place the 127 mm focal length lens on the side of the carrier facing the light source and at a distance of 127 mm from the filament of the bulb. 2. On the photometer, slide the switch all the way to "battery test" this first time. When you are satisfied that the battery is good, return the switch to the "on" position. Check to make sure that the calibration control is set to "cal" and the zero control is centered. The photometer measures the intensity of light applied on it. The instrument will provide an output voltage directly proportional to the intensity. To measure this voltage, and therefore the intensity of the incident light, connect the Data Logger voltage probe to the photometer. Turn the light source on. Start Logger Pro from your computer’s desktop. Click Collect any time you want to measure the intensity in the incident light on the photometer. 3. With none of the polarizers in the light path, adjust the translator and lenses to maximize the photometer reading. Select the sensitivity scale on the photometer that will give you the largest signal without going off the scale. You must use the same scale for the rest of the experiment. 4. Collect a data set for the intensity of the light beam without any of the polarizers. To get average intensity (voltage) go to Analize on the top menu and select Statistics. Record the mean value on Table 1. Put your hand between the light source and the Translator to block the incident beam. Collect the intensity data set and record the mean value on the table. This value measures the intensity due to sources other than the beam; therefore we need to subtract this amount from all the other measurement on the table. Collect a data set for the intensity of the light beam with Polarizer A, then with Polarizer B (with the motor ON) and finally with Polarizer C. NOTE: When the motor of Polarizer B is ON, it will complete one rotation every 4 seconds (or 90 degrees per second.). Expect to see small fluctuations in its intensity profile. Record the mean value for each case on Table 1 and complete the rest of the table. Turn the motor off. TABLE 1 Polarizer Measured Volts Adjusted Volts Percent Transmission None 100% Beam Blocked 0 V 0% Polarizer A Polarizer B (with motor ON) Polarizer C 5. What percent transmission did you expect to observe for the polarizers? Expected transmission % How did the calculated values compare to the result you would have expected? Angular position for the refracted beam = Angular position for the reflected beam = Angle between the reflected beam and the refracted beam = Use Brewster's law to find the index of refraction for the Lucite. n = Compare this value to the value you calculated from Experiment 1 by calculating the percent difference between the two values. % difference = 12. Finally, let us look at one strange effect that some crystals have on light. Remove all items from the optical rail. Configure the laser, 127 mm focal length lens (L1), calcite crystal (CC), and 48 mm focal length lens (L2) as shown. The calcite crystal is at the focal point of each lens, making the separation of the lenses about 175 mm (48mm + 127mm). You should see two images on the wall. If there is only one image or none at all, move the calcite crystal around to make sure you are not hitting a defect in the crystal. Place a polarizer in the beam after L2 and rotate it through 360 degrees. CC LASER L1 L2 127mm 48mm What do you conclude about the polarization of the two beams? Explain.