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EE119 Lab 1: Properties of LightProfessor: Jeff Bokor GSI: Julia ZaksWeek of February 3, 2009ObjectiveThe purpose of this lab is to demonstrate various ways that light can be viewed: as rays, waves,and particles. We will also investigate the polarizations of light. The lab consists of four smallexperiments.1 Light as a RayExperimental SetupUsing a visible laser (HeNe 632.8nm) and a cylindrical lens, construct an optical system to fo custhe beam horizontally while spreading it out vertically. Attach a triangular glass prism to awhite paper and place the prism in the light path. By rotating the prism, you should be ableto see how the beam traverses the prism. Note the incident angle, reflection, and refraction atthe air-glass interfaces as well as the total angle of deviation.Discussion Questions:1. As you rotate the prism, the exit beam should disappear at a certain point. What causesthis? What angle of incidence leads to this?2. If blue light was used instead of red light, how would this affect how the light traversesthe prism?3. At what angle of incidence is the deviation minimized? Does this agree with what you’vecalculated?4. What do you notice about the path of the beam when the angle of deviation is minimized?5. With this lab in mind, what is one method to determine the index of refraction of anunknown transparent material? How would you determine the dispersion of a material?2 Light as a Wave2.1 Experimental SetupPlace a white card about 2 meters from a visible laser source (HeNe laser). Obtain three varioussized pinholes, with diameters roughly on order of the wavelength of light.12.2 Discussion Questions1. What do you predict will happen when you place a pinhole in the path of the light?(Confirm your guess by doing so.)2. What do you predict will happen when you place a pinhole with a slightly larger diameter?(Confirm your guess by asking your TA.)3. What causes this? What does this lead you to believe about the nature of light?3 Light as a ParticleExperimental SetupObtain a photo-multiplier tube and an oscilloscope. (The tube should be configured to allowapproximately one photon in per millisecond with the room lights on, and the oscilloscope shouldbe configured to observe this quantized effect.) Your TA will give a brief introduction to howthe photo- multiplier tube works.Discussion Questions1. How does the light in this experiment behave differently than in the last one?2. If you were to only shine light of a higher energy (i.e. x-rays) or only light of a lowerenergy (i.e. microwaves), what would you notice about the photon count?4 S- and P-PolarizationsExperimental SetupUsing three linear polarization filters, one half-wavelength plate, a glass microscope slide, and aHeNe laser, examine the properties of polarized light and polarization filters.Discussion Questions1. Place one linear polarization filter in the path of a HeNe laser beam and observe theintensity of the laser spot on the wall. Also rotate the filter and observe the intensity.What happens? What can you say about the polarization of the HeNe laser beam?2. Add one more linear polarization filter to the setup for part (a). Rotate the secondpolarization filter so that its polarization axis makes 90 with that of the first filter. Whathappens to the laser spot on the wall? Why?3. Now add third linear polarization filter between the first and the second filters, with itspolarization axis at 45 with that of the first filter. What happens to the intensity of theexit beam?4. Now replace the third filter that you added in part (c) with a half- wavelength plate.What happens? Rotate the half-wavelength plate and observe the laser spot intensity onthe wall. What does the half- wavelength plate do?25. Lets find out if the Brewsters angle really exists. Place a glass slide in the path of theHeNe laser at its Brewster angle. Place and rotate a linear polarization filter in the pathof the reflected beam. What happens? What can you say about the polarization of thereflected


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Berkeley ELENG 119 - Lab 1 Properties of Light

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