� 2d m m The Fabry Perot interferometer can also be used to measure the

# ? 2d m m the fabry perot interferometer can also be

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interference pattern which can be used to determine the wavelength of the light. λ = 2d m / m The Fabry-Perot interferometer can also be used to measure the wavelength of light, with a slightly different methodology from the Michelson interferometer. In this interferometer, two partial mirrors are aligned parallel to each other, forming a reflective cavity. One beam of light from the light source enters this cavity, and reflects back and forth inside. At each reflection, part of the original beam is transmitted, and therefore the incident beam is split into a series of rays. Because all these rays are split from the same original incident beam, they all have a constant phase relationship, which depends on the angle which the beam enters the cavity and the distance between the two mirrors of the cavity. Moving one of the mirrors with respect to the other causes a phase shift, and therefore a shift in the interference pattern. When the mirror moves by half a wavelength of the light source, the interference pattern becomes identical to the original, which is the same as for the Michelson interferometer. The wavelength of the light source can be calculated with the same equation as for the Michelson interferometer, with d m being the distance between the two mirrors of the reflective cavity. When light travels through a medium, the wavelength of the light varies according to the index of refraction of the medium. Another way to change the phase relationship between interfering waves, in addition to changing the distance of the optical path, is to change the medium in which the light passes through. This method can be used to calculate indices such as the index of refraction of air. The index of refraction of a solid substance such as glass can be measured using an application of Snell’s Law, which describes the bending of light by an angle measurement as it travels through media of different indices of refraction. EXPERIMENTAL Materials The equipment used in this experiment to measure the wavelength of the laser light and the index of refraction of air and glass was the interferometer and its corresponding components (mirrors, beam Michael Lin Tuesday Section Partners: Josh Narciso, Bryant Rolfe Due Date: 3/7/07 splitter, viewing screen, etc.) Experimental Method Before the experiment the laser was warmed up and aligned with the interferometer. The interferometer was then setup for the Fabry-Perot method according to Figure 6.3 in the lab manual, and the wavelength of the laser light source was calculated by observing changes in interference patterns. Then the interferometer was readjusted for the Michelson method according to Figure 6.2 in the lab manual, and measurements were taken again to measure the wavelength of the light source.  #### You've reached the end of your free preview.

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• Spring '08
• CARLO
• Diffraction, Light, Wavelength, Michelson interferometer, light source
• • • 