4.5.4 Experimental procedures
1)Observing the polarization and extinction of light by using a polarizer
(1)Polarization observation:Illuminate the laser beam onto the screen,insert a polarizer perpendicular to the laser beam propagation direction,and rotate the polarizer to observe the changes in the intensity of the transmitted light.
(2)Extinction observation:add a second polarizer(called analyzer)between the first polarizer and the screen perpendicular to the laser beam propagation direction,fix the first polarizer and rotate the second polarizer in a plane perpendicular to the laser beam to observe the phenomenon.
2)Generating polarization of light by Reflection and refraction
(1)Mount the high-brightness small light source,the multi-slit plate,the convex lens(f=150 mm),and the optical goniometer on the optical bench,respectively;adjust the coaxial height and make the slits on the focal plane of the lens.
(2)The black glass mirror is installed in the center of the optical goniometer;the polarizer holder is installed on the rotating arm,and the light beam must be parallel to the glass plate.
(3)Rotate the platform through the angle θ(α+θ=90°,which is the incident angle)to form reflected and transmitted beams.
(4)Use an analyzer to check the polarization state of the reflected light and determine the direction of the transmission axis of the analyzer.
(5)When turning to a certain angle,rotating the analyzer can observe the phenomenon that the light vibration perpendicular to the incident surface is eliminated.At this time,α is the Brewster angle,and record the value of the incident angle at this time.
3)Obtaining circularly and elliptically polarized light;distinguishing circularly polarized light,natural polarized light,elliptically polarized light,and partially polarized light.(https://www.daowen.com)
(1)Install two polarizers A and B on the optical bench,adjust the positions of the polarizers A and B to make the passing light disappear,and then insert a 1/4 wave plate C1.(Pay attention to make the light pass through the center of the component as much as possible).
(2)Rotate C1 with the light as the axis to make the transmitted light to extinction,and then rotate B in the range of 360° to observe the phenomenon.
(3)Then turn C1 from the extinction position through 30°,45°,60°,75°,90°,and then turn B to 360° every time around the light axis to observe and record the phenomenon.(When is circularly polarized light generated?When is elliptically polarized light generated?)
(4)Discrimination of circularly polarized light,natural polarized light,elliptically polarized light,and partially polarized light:add a 1/4 wave plate C2 in the middle of C1 and B,and then follow the above steps to observe and record the phenomenon.Summarize the identification methods of circularly polarized light,natural polarized light and elliptically polarized light,and partially polarized light.
4)Verifying Malus’law
Install the instrument on the optical bench so that the beam emitted by the laser passes through the polarizer A and the analyzer B and incidents to the silicon photocell P,so that A and B are orthogonal,and record the value shown on the galvanometer.Record every rotation of the analyzer(10°～15°)until it rotates 90°,repeat 3 times.
5)Examining the influence of half-wave plate on polarized light
(1)On the basis of the above experiment—verifying Malus’law,adjust A and B to be orthogonal,place a half-wave plate in parallel between A and B,take the light direction as the axis,turn the half-wave plate 360°,and record the times of extinctions and the angle of B.
(2)Make A and B orthogonal,the optical axis of the half-wave plate and the main section of A form an angle of α(10°～15°),rotate B to make the transmitted light to extinction again,and record the angle of B.Change the angle α with an increasing degree by 10°～15° each time,and measure the data until α=90° as above.
