University of California, Berkeley Spring 2007EECS 117 Prof. A. NiknejadEECS 117 Demonstration 6Plane WavesNAMEWARNING: SAFETY FIRST! ALWAYS WEAR SAFETY GOGGLES WHENLASER IS ON. DO NOT ALLOW THE LASER BEAM, EITHER DIRECTLYOR AFTER REFLECTION FROM A SURFACE, TO ENTER ANYONE’SEYE. PERMANENT BLINDNESS MAY RESULT.Introduction. Polarization, reflection and refraction of plane electromagnetic waves aredescribed in Inan Chapter 8 . In this demonstration you will examine these phenomena forlight waves, using a He-Ne laser as a source of electromagnetic waves (light) at wave-length632.8 nm (red light).You will study Snell’s law, total internal reflection, and Brewster’s angle, and their po-larization properties. The experiment is shown below:1 m. DIA"CELETEX" TABLEθ 2θ1θ1SEMICIRCULARLENS L1 (Acrylic, n =1.49)6 1/2" HIGHCARDBOARD FACEPOLARIZER P2SCREEN W1HOLE INCARDBOARD FACESUPPORTTABLE S1POLARIZER P1LASERHANDLE ALL OPTICAL COMPONENTS WITH CARE. DO NOT TOUCHTHE OPTICAL SURFACES WITH YOUR FINGERS.Procedure:1. Examine the LAS-101 HeNe laser. Note the gas discharge tube, Brewster’s angle win-dows, and high reflectivity (for red light) mirrors. View the white light in the roomthrough the mirrors. What color do you see, and why?2. Turn on the laser. Direct the beam through the hole in the cardboard face towardthe rotating support S1. Place polarizer P1 between the laser and the cardboardface. To determine whether the laser beam is polarized, observe the amplitude ofthe transmitted beam on screen W1 as the polarizer is rotated within its holder. Ifthe beam is polarized, the amplitude of the transmitted beam will change. Is thelaser beam polarized?. Next place polarizer P2 between the screen and thecardboard face, and use P2 to detect the polarization produced by P1. Minimumtransmission results when the polarizing directions of P1 and P2 are at right angles.3. Snell’s law. Remove the polarizers. Place lens L1 (index of refraction = 1.49) on sup-port S1, centered so that the laser beam is incident on the flat surface of L1 at thecenter of curvature. This alignment should be done carefully. The beam should exitthe lens perpendicular to its surface. Rotate S1 and verify Snell’s law [Sec. 6.11, eq.(3)] for a few angles of incidence:θ1= ; θ2(measured) = ; θ2(Snell’s law) = .θ1= ; θ2(measured) = ; θ2(Snell’s law) = .Insert P1 and vary the polarization. Does Snell’s law depend on the polarization?.4. Total internal reflection. Remove the polarizers. Rotate S1 so that the laser beam isincident on the curved surface of L1. Rotate S1 and observe the angles and amplitudesof the waves tr ansmitted and reflected from the flat surface of the lens L1. When theangle of incidence (on the flat surface) reaches the critical angle θcfor total internalreflection, the transmitted wave emerges parallel to the flat surface of L1. For θ > θc,the transmitted beam disappears, and all incident wave energy is reflect ed. Measurethe critical angle and compare with the theoretical value.θc(measured) = ; θc(theory) = .Insert P1. Does the phenomenon of total internal reflection depend on the polariza-tion?.5. Brewster’s angle. Insert P1 with the plane of polarization lying in the plane of incidence(E field parallel to the table.) Rotate S1 so that the laser beam is incident on the flatsurface of L1. Examine the reflected wave as you vary the angle of incidence θ1byrotating S1. When θ1is equal to Brewster’s angle θp, then th e reflected beam willvanish. Verify this. Measure Brewster’s angle and compare with the theoretical value.(You can remove the polarizer to measure the angle):θp(measured) =; θp(theory) = .2Repeat the above with the E field perpendicular to the plane of incidence (E fieldperpendicular to the table). Is there a Brewster