An experimental method for determination of the refractive. The michelson interferometer is an extremely versatile instrument that can be used to. Pdf direct measurement of the absolute light refractive index of air. Record the le pressure, and nd p, using 101kpa as the starting pressure. That is, the frequency w is the same, but the wavevector k becomes nk. This is a lab experiment demonstrating the lines of an interference pattern measuring the refractive index of air, with the aid of a pressure vessel in one arm. Measuring the index of refraction of air in order to measure the index of refraction of air, the pressure in a vacuum cell located in one of the arms of the interferometer will be reduced and the number of fringes will be counted, however in this case the moving mirror will remain fixed as the pressure is varied. Measuring the refractive index of infrared materials by. P is linearly proportional to the change in index of refraction.
M1 and m2 are two plane mirrors silvered on the front. The air was let slowly back in by the person counting the fringes, they also counted out the fringes as they passed. Introduction a michelson interferometer is a device used to measure very small distances by observing the. Manual includes illustrated setup instructions, a detailed discussion of basic michelson interferometry plus two copyready experiments measure the wavelength of monochromatic light and measure the index of refraction of air. In this experiment you will measure the index of refraction of air by comparing the optical path lengths of two columns of air of equal physical length but at different pressures. Figure \\pageindex1\ depicts the interferometer and the path of a. Over a 1 k temperature range an agreement on the level of 5. The change in optical path length of the right hand beam is 2 x 5 cm x n air 1 n. Origin of the index of refraction of a material medium 1 the apparatus 4 the michelson interferometer 4 gashandling system 8 fringecounting electronics 9 prelab problems 12 procedure initial setup data collection 14 data analysis 15. Schematic illustration ofa michelson interferometer. Introduction to the michelson interferometer the michelson interferometer used in this experiment was built and used in the following form. Wavelength and refractive indices from interferometry.
Each of those light beams is reflected back toward the beamsplitter which then combines their amplitudes using the superposition principle. Using a michelson interferometer to measure the index of. Index of refraction of air measurement the speed of light through a material depends on the index of refraction of that material. Read the textbook description of the michelson interferometer given in our textbook, pages 977978. To adjust the michelson interferometer so that circular, straight line and white light fringes can be observed. The air from the cell will be removed and this changes the refractive index,n. Pdf on jan 1, 2017, jozef babiak and others published direct measurement of the absolute light refractive index of air with the made double michelson interferometer find, read and cite all the. It has made it possible to create optical systems that are accurate to within a fraction of a wavelength.
Finally, the index of refraction was measured for light passing through a plane of glass ng 1. The basic idea is to split a beam of light into two beams. Two weights for all experiments with michelson interferometer and one. When set up correctly the michelson interferometer is used in conjunction with a gas cell and vacuum pump to investigatethe dependence of the refractiveindex of airon the pressure and to simply measure the refractive index of air. One possible application is the measurement of the refractive index of a thin parallelside plate of transparent material of known thickness. Michelson interferometer, gas cell, compensator, absolute pressure gauge, cylinder with helium gas, vacuum pump. Lets assume that the shift is linear and extrapolate the data to determine. A michelson interferometric technique for measuring refractive index of sodium zinc tellurite glasses deepak n.
Nov 06, 20 the refractive index of air with the air cell in the uncompensated leg. Experiment 4 the michelson interferometer 2 figure 1. Air refractive index measurement using lowcoherence. The introductory michelson interferometer provides precision interferometry at an economical price. Index of refraction n of air introduction in this experiment you will measure the index of refraction of air by comparing the optical path lengths of two columns of air of equal physical length but at different pressures. The first section of the lab was to correctly configure the michelson interferometer and to achieve proper alignment of the laserinterferometer setup so that the fringe pattern was easily visible.
Schematic illustration of a michelson interferometer. Interferometer suppose the micrometer knob is turned so it pushes the lever in by a distance d see figure 4. The index of refraction of gasses using a michelson. The index of refraction depends not only on the composition of the gas but also on the frequency of the light, so you will perform measurements using both a red laser and a green laser. The michelson interferometer department of physics. The basic elements of a michelson interferometer are shown in fig. From these data, find the index of refraction of air at atmospheric pressure. Two weights for all experiments with michelson interferometer and one weight more for experiments with fabryper. Jan 20, 2020 the michelson interferometer invented by the american physicist albert a. The michelson interferometer is illustrated in fig. The michelson interferometer and the hene laser university. To investigate how changes in pressure affect the index of refraction of air. Alternatively, if the refractive index is known, the thickness of the plate may be.
On the use of a michelson interferometer to determine. In this study, the michelson interferometer was used to measure wavelength of light. Theory the main features of the interferometer are shown schematically in figure 1. Now the light wavelength in a medium of index of refraction n is 0 n where 0 is the wavelength in vacuum. To use the interferometer to measure the index of refraction of air. Using a michelson interferometer to measure the index of refraction of air kimberly belmes, carly stau er department of physics, paci c lutheran university tacoma, wa 98447 october 2, 2017 october 23, 2017 abstract using a michelson interferometer, we experimentally measured the index of refraction of air, n air. The refractive index of liquid so 2 laser beam splitter mirror mirror cell rotatory stage photodiode computer stage controller figure 1.
The michelson interferometer invented by the american physicist albert a. In the michelson interferometer, the characteristics of the fringe pattern depend on the phase relationship between the two interfering beams. Michelson, 18521931 is a precision instrument that produces interference fringes by splitting a light beam into two parts and then recombining them after they have traveled different optical paths. The interferometer was set up with the mercury lamp with the mercury green lter. Interferometer interference pattern measuring refractive.
A standard michelson interferometer mi has been utilized to measure the. Pdf group refractive index measurement by michelson. Pdf direct measurement of the absolute light refractive. This experiment with the michelson interferometer will involve. Theory in 1887, albert michelson built his interferometer originally to investigate the existence of ether, which was believed to permeate all space. Group refractive index measurement by michelson interferometer. The refractive index of air with a michelson interferometer. In this way the group index of optical materials fused silica and schott glass f3 was measured with an accuracy of 10. Iyer a thesis presented to the graduate and research committee oflehigh university in candidacy for the degree of master ofscience in electrical engineering lehigh universitv december 2006. An experimental method for determination of the refractive index of liquid samples using michelson interferometer. Pdf measurement of index of refraction of air and carbon. Twymangreen the twymangreen interferometer is an important contemporary tool for testing optical components. Determination of the refractive index of a glass block.
Twymangreen test of optical components qualitatively 1. The refractive index of air is accurately measured using a vacuum cell and a tandem lowcoherence interferometer with a communication optical fiber of 30 km length with standard uncertainties of 0. We will construct a michelson interferometer, study the fringe patterns resulting from both a point source and a parallel beam. Department of physics and astronom y, university of sheffield second year laboratory 1 aims the main aims of this experiment are first, to use the michelson interferometer to measure the refractive index of samples of glass and mica and air and second, to identify three unknown gases on the basis of the value of their refractive index. The refractive index of air na is determined mainly by wavelength, atmospheric pressure, temperature and humidity 18. The index of refraction of gasses using a michelson interferometer introduction 1 theory. These are basic optical tools used to precisely measure wavelength, distance, index of refraction, and temporal coherence of optical beams etc. On the use of a michelson interferometer to determine indices of refraction john grasel 5082011 abstract the index of refraction of helium gas was measured by recording the number of fringes traversing the output of a michelson interferometer as the helium pressure in an optical cell increased. An advantage of using fabryperot interferometry exclusively is that it is not as affected by vibrations and air currents as the michelson interferometer. They are conveniently divided into two main classes. Measurement of refractive index and thickness of transparent. You will need to spend some time in the library doing some research for this aspect of your notebook. When a gas is allowed to slowly fill the container, a total of 236 dark fringes are counted to move past a reference line. Suppose the gas with the index of refraction n is admitted into it.
To calibrate the mirror movement using a hene laser. Michelsons interferometer refractive index of glass plate. Michelson interferometer is a widely used instrument for measuring wavelength of light, refractive index of transparent materials etc. Suppression of air refractive index variations in high.
Pdf measurement of index of refraction of air and carbon dioxide. The michelson interferometer is a common configuration for optical interferometry and was invented by albert abraham michelson. It is an amplitudesplitting interferometers devised by albert michelson in 1890, the first american physicist to receive the nobel prize 1907 for work in optics. Consider a thin glass plate of thickness t and refractive index n, inserted normal to the path of one of the two interfering beams in michelson interferometer. Themichelsoninterferometer simon fraser university. The schematic setup for the michelson interferometer is going to be.
A shift of m fringes will occur when the refractive index changes as air is taken out of the cell. Using a beam splitter, a light source is split into two arms. In this lab we measure the wavelength of light from a helium neon laser, the index of refraction of air, and the thermal coefficient of expansion of copper. The method has been experimentally tested in comparison with the indirect measurement of the refractive index of air in a thermal controlled environment. Pdf on oct 27, 2012, joseph vermont bandoy and others published measurement of index of refraction of air and carbon dioxide using michelson interferometer find, read and cite all the research. Phy 4264l michelson interferometer optics lab 410 figure 3. If the fringe pattern moves slowly back and forth, it is due to air currents in the room. The refractive index also depends on the wavelength colour of the light ray. Michelsons interferometer refractive index of glass. Introductory michelson interferometer os8501 products. This effect is the origin of the index of refraction of a transparent material. M1 and m2 are two plane mirrors silvered on the front surfaces. Then slowly pump the air out of the cell, counting the number of fringe transitions as this is done. In the case of an empty cuvette, the refractive index of air can be measured using eq.
This technique allows us the determination of the refractive index of a given liquid or a transparent sample accurately to high precision, with an accuracy limited only by the precision in the. A michelson interferometric technique for measuring. Figure \\pageindex1\ depicts the interferometer and the path of a light beam from a single point on the extended. A michelson interferometric technique for measuring refractive index. The optical path length of the beam through the plate is nt, while the optical path length through an equal thickness of air is just t. This experiment seeks to use the michelson interferometer to perform several precision measurements, namely to calculate the refractive index of air, to investigate the dependence of this index on air pressure, to measure the wavelength difference of a sodium doublet, and finally, to measure the band pass of a wavelength filter. In an interferometer figure 1 a light beam in this. They are mounted vertically on two rigid holders placed at the sides of a flat metal stand. This can be done by setting up a simple proportion. In this diagram, refraction is ignored and antiparallel rays are slightly displaced for the sake of clarity.
If one of our interferometry beams passes through a section of vacuum while the other traverses only through air, the beams will end up additionally out of phase. Changing the pressure of gas in the cell alters path length. Michelson designed and built an interferometer based on the interference principle similar to that used in youngs double slit experiment details will be discussed in the lecture class. Aug 02, 2011 errors caused by different position of the interferometer laser beam and air sensors are thus eliminated. In this experiment the famous michelson interferometer and some of its uses are investigated. Michelson the michelson interferometer is historically important, and also provides a simple interferometric configuration for introducing basic principles. Evacuating the air from the chamber causes a shift of 60 fringes. Michelson interferometer, the refractive index of a gas goal. To determine the refractive index of a thin glass plate. Introduction interferometers are devices employed in the study of interference patterns produced by various light sources. In your lab notebook leave space for an introduction that describes the michelson interferometer. Twymangreen the twymangreen interferometer is an important.
The instrument used to compare optical path lengths is the michelson interferometer. Pasco scientific 01205187c precision interferometer is used in michelson mode to investigate wavelengths and refractive indices. Refraction index of air and co2 with michelson interferometer. The main features of the interferometer are shown schematically in figure 1. It was used to quantify the index of refraction of carbon dioxide co2 gas at. Pdf on jan 1, 2017, jozef babiak and others published direct. A change in pressure causes a change in index of refraction. The michelson interferometer has long been a popular piece of equipment in the physics undergraduate laboratory.
Michelson interferometers can be used to find out the refractive index of glass plates or thin films. The michelson interferometer is a historically important device which provides simple interferometric configuration for introducing basic principles. Setup a vacuum cell is placed along one path of a michelson interferometer. Measurement of refractive index using a michelson interferometer. A recently developed method which allows for the measurement of the index of refraction of semiconductor wafers is an adaptation to the michelson interferometer that combines both michelson and fabryperot interferometry 4. Refraction index of air and co 2 with michelson interferometer 2 22207 phywe series of publications laboratory experiments physics phywe systeme gmbh 37070 gottingen, germany pressure in the cuvette is gradually reduced with the manual pump. Students can measure the wavelength of light and the indices of refraction of air and other substances. On the use of a michelson interferometer to determine indices. During this process, the interference rings draw togeth. This device works under the principle of interference. Finally, using a pressure vessel, the index of refraction of air as a function of pressure was measured. Measure the refractive index of gases using a michelson interferometer equipment. It is su cient to reduce the pressure down to about 50kpa. A michelson interferometer illuminated by a polychromatic light source was used to measure the time of flight of a light pulse or intensity substructure through a sample of optical material.
Interferometry, michelson and fabryperot interferometer. The index of refraction of air the index of refraction of co 2 report these values, their errors, and your results from investigating the lever assembly. Measuring the refractive index of infrared materials by dual. The michelson interferometer university of sheffield. The michelson interferometer equipment preparation goals.
The first section of the lab was to correctly configure the michelson interferometer and to achieve proper alignment of the laser interferometer setup so that the fringe pattern was easily visible. The michelson interferometer has long been a popular piece of equipment in the physics under graduate laboratory. Experiment 8 michelson interferometer 1 introduction. Screws are provided in front of the holders, adjusting of which. Michelson interferometer is its sensitivity to vibrations and air currents 4.
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