lab1_michelson - PHY 252 Lab 1 The Michelson Interferometer...

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PHY 252 Lab 1: The Michelson Interferometer Fall 2009 To better understand the interferometer used by Michelson and Morley, we will use a simpli- fied version of their instrument to calibrate the motion of a micrometer, and then to measure the refractive index of air. The basic idea of the interferometer is shown in Fig. 1. The light from a (nearly) monochro- matic source is split into two beams which recombine to form a visible pattern of areas of construc- tive and destructive interference; i.e. , bright and dark fringes. When the effective length of one of the optical paths is changed by some means, then any given point on the interference pattern shifts from light to dark or vice-versa for each half-wavelength of path length change. As a general rule: treat the equipment with respect so that it remains in good shape for the students that follow you. Don’t touch mirror surfaces, treat equipment gently, and so on. Also, never look directly into the beam or its reflection! There’s a laser safety classification scheme; see for example If you consult this web page, you will learn that the lasers used for this lab will not cause permanent damage even if accidentally directed at someone’s eye. However, it can be very uncomfortable, it can affect vision over a short period of time, and besides it’s just poor practice in case you work with more powerful lasers later on. With more powerful lasers, you have to wear goggles that block out the narrow wavelength range that the laser operates in, and use other precautions. So, always use care when working with lasers, and also make it your own responsibility to understand safe procedures in addition to getting trained in the safe practices of the lab you work in. To get fringes, you must make the two beams land on top of each other. Here’s a suggested procedure to get there, based on the sketches of Figs. 1 and 2 as well as the photo of Fig. 3: 1. In the end you’re going to want to see the fringes projected on a surface. A good way to set things up is to use a wall as the viewing screen; a sheet of white paper on a book will work
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This note was uploaded on 05/28/2011 for the course PHY 251 taught by Professor Rijssenbeek during the Fall '01 term at SUNY Stony Brook.

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lab1_michelson - PHY 252 Lab 1 The Michelson Interferometer...

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