DOC PREVIEW
AUGUSTANA PH 202 - Ray Optics and Polarization

This preview shows page 1-2-3-4 out of 12 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 12 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 12 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 12 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 12 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 12 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

IntroductionName: _________________________________ Lab Section: _________ Group Number: __________Lab Partners: _______________________________________________ Grade: ____________Physics 202Lab 7Ray Optics and PolarizationPre-Lab 1) In question 3 in the lab, what will you plot as y and x? Write down how you will obtain the error bars in your y-values. If you will propagate error, write down the specific error propagation equation here.2) Fill a glass with water. Look down through the water, and then through the glass to your hand on the outside. Can you see it? Tip the glass towards you and watch your hand disappear. Why? Do you know what physical phenomena this observation is related to in this lab?3) Draw a picture of a polarized and unpolarized E-field (go ahead and just do it at one point in space using 1an arrow(s)). Polarized means that the E-field oscillates perpendicularly at a fixed orientation relative to the direction of propagation. See the book (or notes) for help. 4) Predict an answer to question 8. For your prediction, a picture or math will do. For the lab you hand in, you will need to do both. Name: _________________________________ Lab Section: _________ Group Number: __________2Lab Partners: _______________________________________________ Grade: ____________Physics 202Lab 7Ray Optics and PolarizationIntroduction Light is the visible part of the electromagnetic spectrum, and like all electromagnetic (EM) waves, originatesfrom accelerating charge. A simple model of EM wave generation that goes quite far is an analogy to anoscillating mass on a spring. The mass in this case is an electron or charged part of a molecule, and thespring is the bond to the nucleus to which the charge is attached. Simple harmonic motion of a chargegenerates a sinusoidal EM wave. If the wavelength is between 400 nm and 700 nm we observe it as light. Figure 1 is a typical schematic used to represent a wave. Imagine you are looking at ripples on a pond (anaerial view). This could be represented by Fig. 1. The lines denote the crests of the wave. The center betweentwo lines represents a valley, and you have to use your imagination to see every height in between a crest anda valley. The distance between two crests or two valleys is a wavelength, . The wave in Fig. 1 is a specialkind of wave called a plane wave. We like simple pictures and so we will just leave the arrow to denote aplane wave. Figure 2 is the ray-optics schematic for reflection and refraction at the interface of a dielectric (non-conducting material). The line drawn perpendicular (or 90º) to the interface is called the normal. All angles are calculated from the normal line. The law of reflection states “the angle of incidence equals the angle of reflection.” 3Figure 1: Schmatic of a plane waveFigure 2: Reflection and Refraction at adielectric interface.i rq q=(1)Snell’s Law which relates the incident ray to the refracted ray is:sin sini i t tn nq q=(2)where nt is the index of refraction of the material of transmission (the material the light is entering), and nithe index of refraction of the incident material (the material from which the ray is coming) . The index is thefactor by which the speed of light, c, is slower in materials than in a vacuum, vcn  (smxc8103). Theindex of air is approximately 1.00. The index for vacuum is exactly 1. Note that the power of the sum of thepower transmitted and reflected is equal to the power incident.If the incident ray of light is going from a material of larger index (slower) to one of smaller index (faster),there is a critical angle for which all of the light is reflected back into the incident medium.itcnnsin(3)This phenomenon is referred to as total internal reflection is the reason light can be guided inside the smallhigher-index core of glass optical fiber. Finally, another important aspect of electromagnetic waves you will be exploring in the followingexperiments is polarization. Figure 3 shows an example of a sinusoidal electric field. An oscillating magneticfield always accompanies an oscillating electric field (you can’t have E without the M in an EM wave).However, in Figure 3, the magnetic field has been omitted for clarity. Figure 3: Schematic of a polarized EM wave and the effect it has on The arrows in Fig. 3 represent the strength of the electric field at a given point in space. As the travelingwave hits the charge, the charge will move in the direction of the arrow. If the arrow is big, the charge isdisplaced a lot. If the arrow is small, the charge is displaced a little (convention says arrow denotes thedirection a positive charge would move so technically the charge moves opposite the direction of the arrow).How quickly the charge responds to the incident wave is what is responsible for the index of refraction in amaterial. This is how light can be slowed to 20 mi/hr. When the mass shakes up and down at a resonancefrequency, this corresponds to energy given up to the material in the form of heat (absorption).4Note how the E-field has a direction and the charge cares about it. For example, if you rotated the mass-spring system 90 degrees (coming out of the page at you), the charge wouldn’t move up and down since thearrows don’t line up with the spring. The E-field would have no effect on the charge. Likewise, we couldmake a device that burned up the part of the energy of the E-field in one direction so that we could polarize itin the direction we wanted.By passing light through a polarizer, a light beam with known electric field direction, or polarization state,can be prepared. If a beam of polarized light is incident upon a polarization analyzer the transmittedintensity obeys Malus’ Law:20cosI I q=(4)where I0 is the maximum transmitted intensity, and  is the angle between the incident light’s polarizationdirection and the axis of the analyzer. One useful special case is that the intensity drops (0)2/1( II ) whenunpolarized light (E-field in every direction, not just one) passes through a polarizer.The goal for today’s lab is to experimentally verify each formula. You will develop your method for provingeach formula and demonstrate the validity of these equations with graphs.Part I: Reflection and Refraction Mount the ray table and the light source on the optics bench as shown in Figure 4. Power the light source.The light source should be oriented so that the multiple slits


View Full Document

AUGUSTANA PH 202 - Ray Optics and Polarization

Download Ray Optics and Polarization
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Ray Optics and Polarization and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Ray Optics and Polarization 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?