Interferometer suppose the micrometer knob is turned so it pushes the lever in by a distance d see figure 4. Record the le pressure, and nd p, using 101kpa as the starting pressure. Suppose the gas with the index of refraction n is admitted into it. We will construct a michelson interferometer, study the fringe patterns resulting from both a point source and a parallel beam. 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. In the michelson interferometer, the characteristics of the fringe pattern depend on the phase relationship between the two interfering beams.
Using a michelson interferometer to measure the index of. The refractive index of air na is determined mainly by wavelength, atmospheric pressure, temperature and humidity 18. When a gas is allowed to slowly fill the container, a total of 236 dark fringes are counted to move past a reference line. Twymangreen the twymangreen interferometer is an important contemporary tool for testing optical components. To use the interferometer to measure the index of refraction of air. The air was let slowly back in by the person counting the fringes, they also counted out the fringes as they passed. 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 this study, the michelson interferometer was used to measure wavelength of light. 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. Then slowly pump the air out of the cell, counting the number of fringe transitions as this is done. 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. An experimental method for determination of the refractive. Experiment 4 the michelson interferometer 2 figure 1. Jan 20, 2020 the michelson interferometer invented by the american physicist albert a.
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. One possible application is the measurement of the refractive index of a thin parallelside plate of transparent material of known thickness. Determination of the refractive index of a glass block. You will need to spend some time in the library doing some research for this aspect of your notebook. A michelson interferometric technique for measuring refractive index of sodium zinc tellurite glasses deepak n. Michelsons interferometer refractive index of glass plate.
Using a beam splitter, a light source is split into two arms. Two weights for all experiments with michelson interferometer and one weight more for experiments with fabryper. Changing the pressure of gas in the cell alters path length. To investigate how changes in pressure affect the index of refraction of air. Interferometer interference pattern measuring refractive. A michelson interferometric technique for measuring.
The michelson interferometer has long been a popular piece of equipment in the physics undergraduate laboratory. 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. Pdf direct measurement of the absolute light refractive index of air. Michelson interferometer is a widely used instrument for measuring wavelength of light, refractive index of transparent materials etc. In this experiment the famous michelson interferometer and some of its uses are investigated. The michelson interferometer is a historically important device which provides simple interferometric configuration for introducing basic principles. Phy 4264l michelson interferometer optics lab 410 figure 3. Experiment 8 michelson interferometer 1 introduction. In this way the group index of optical materials fused silica and schott glass f3 was measured with an accuracy of 10. Read the textbook description of the michelson interferometer given in our textbook, pages 977978. 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. They are conveniently divided into two main classes.
Group refractive index measurement by michelson interferometer. Introduction to the michelson interferometer the michelson interferometer used in this experiment was built and used in the following form. Each of those light beams is reflected back toward the beamsplitter which then combines their amplitudes using the superposition principle. Interferometry, michelson and fabryperot interferometer. The index of refraction of gasses using a michelson. To adjust the michelson interferometer so that circular, straight line and white light fringes can be observed. This can be done by setting up a simple proportion. Michelson interferometer is its sensitivity to vibrations and air currents 4. The refractive index also depends on the wavelength colour of the light ray. The basic elements of a michelson interferometer are shown in fig. 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. 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. 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. 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.
The index of refraction of gasses using a michelson interferometer introduction 1 theory. 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. M1 and m2 are two plane mirrors silvered on the front. 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. Theory the main features of the interferometer are shown schematically in figure 1. It has made it possible to create optical systems that are accurate to within a fraction of a wavelength. A michelson interferometric technique for measuring refractive index. Finally, using a pressure vessel, the index of refraction of air as a function of pressure was measured. Michelson interferometer, the refractive index of a gas goal. The michelson interferometer invented by the american physicist albert a. The change in optical path length of the right hand beam is 2 x 5 cm x n air 1 n. 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. Pasco scientific 01205187c precision interferometer is used in michelson mode to investigate wavelengths and refractive indices.
Pdf measurement of index of refraction of air and carbon dioxide. The refractive index of liquid so 2 laser beam splitter mirror mirror cell rotatory stage photodiode computer stage controller figure 1. 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. Over a 1 k temperature range an agreement on the level of 5. 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 michelson interferometer department of physics. From these data, find the index of refraction of air at atmospheric pressure. A change in pressure causes a change in index of refraction. On the use of a michelson interferometer to determine indices. 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. Measuring the refractive index of infrared materials by.
A shift of m fringes will occur when the refractive index changes as air is taken out of the cell. The refractive index of air with a michelson interferometer. Pdf direct measurement of the absolute light refractive. Suppression of air refractive index variations in high. M1 and m2 are two plane mirrors silvered on the front surfaces. It was used to quantify the index of refraction of carbon dioxide co2 gas at. Michelsons interferometer refractive index of glass. In your lab notebook leave space for an introduction that describes the michelson interferometer.
To calibrate the mirror movement using a hene laser. These are basic optical tools used to precisely measure wavelength, distance, index of refraction, and temporal coherence of optical beams etc. Finally, the index of refraction was measured for light passing through a plane of glass ng 1. An advantage of using fabryperot interferometry exclusively is that it is not as affected by vibrations and air currents as the michelson interferometer. Figure \\pageindex1\ depicts the interferometer and the path of a light beam from a single point on the extended. Theory in 1887, albert michelson built his interferometer originally to investigate the existence of ether, which was believed to permeate all space. Aug 02, 2011 errors caused by different position of the interferometer laser beam and air sensors are thus eliminated.
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. The michelson interferometer and the hene laser university. Nov 06, 20 the refractive index of air with the air cell in the uncompensated leg. Pdf on jan 1, 2017, jozef babiak and others published direct. Air refractive index measurement using lowcoherence. The michelson interferometer is a common configuration for optical interferometry and was invented by albert abraham michelson. To determine the refractive index of a thin glass plate. Screws are provided in front of the holders, adjusting of which.
The schematic setup for the michelson interferometer is going to be. Measuring the refractive index of infrared materials by dual. Figure \\pageindex1\ depicts the interferometer and the path of a. 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. 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. Themichelsoninterferometer simon fraser university. The main features of the interferometer are shown schematically in figure 1. The michelson interferometer equipment preparation goals. The michelson interferometer has long been a popular piece of equipment in the physics under graduate laboratory. The michelson interferometer is an extremely versatile instrument that can be used to. Pdf group refractive index measurement by michelson. Twymangreen test of optical components qualitatively 1. It is su cient to reduce the pressure down to about 50kpa. The michelson interferometer is illustrated in fig.
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. The method has been experimentally tested in comparison with the indirect measurement of the refractive index of air in a thermal controlled environment. Introduction a michelson interferometer is a device used to measure very small distances by observing the. The instrument used to compare optical path lengths is the michelson interferometer. Twymangreen the twymangreen interferometer is an important. 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. Lets assume that the shift is linear and extrapolate the data to determine. The michelson interferometer university of sheffield.
P is linearly proportional to the change in index of refraction. If the fringe pattern moves slowly back and forth, it is due to air currents in the room. Index of refraction of air measurement the speed of light through a material depends on the index of refraction of that material. This experiment with the michelson interferometer will involve. Refraction index of air and co2 with michelson interferometer. They are mounted vertically on two rigid holders placed at the sides of a flat metal stand.
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. Measurement of refractive index using a michelson interferometer. Schematic illustration of a michelson interferometer. 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. Two weights for all experiments with michelson interferometer and one. The basic idea is to split a beam of light into two beams. Measurement of refractive index and thickness of transparent. Introduction interferometers are devices employed in the study of interference patterns produced by various light sources. An experimental method for determination of the refractive index of liquid samples using michelson interferometer. On the use of a michelson interferometer to determine. 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.
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. Pdf measurement of index of refraction of air and carbon. 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. The interferometer was set up with the mercury lamp with the mercury green lter. Setup a vacuum cell is placed along one path of a michelson interferometer. Alternatively, if the refractive index is known, the thickness of the plate may be. In an interferometer figure 1 a light beam in this. Students can measure the wavelength of light and the indices of refraction of air and other substances. This device works under the principle of interference.
A standard michelson interferometer mi has been utilized to measure the. 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. Wavelength and refractive indices from interferometry. Michelson the michelson interferometer is historically important, and also provides a simple interferometric configuration for introducing basic principles. Measure the refractive index of gases using a michelson interferometer equipment. Schematic illustration ofa michelson interferometer. During this process, the interference rings draw togeth. That is, the frequency w is the same, but the wavevector k becomes nk. Introductory michelson interferometer os8501 products. Michelson interferometer, gas cell, compensator, absolute pressure gauge, cylinder with helium gas, vacuum pump. In the case of an empty cuvette, the refractive index of air can be measured using eq.
The introductory michelson interferometer provides precision interferometry at an economical price. Now the light wavelength in a medium of index of refraction n is 0 n where 0 is the wavelength in vacuum. The air from the cell will be removed and this changes the refractive index,n. 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 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. In this diagram, refraction is ignored and antiparallel rays are slightly displaced for the sake of clarity. Evacuating the air from the chamber causes a shift of 60 fringes. This effect is the origin of the index of refraction of a transparent material.
533 1103 2 350 427 363 139 913 896 1560 833 33 933 1417 1283 644 1 753 58 191 96 1030 714 877 1065 1510 1008 2 1010 476 296 1359 323 1380 1058 561 1565 157 1151 725 405 561 622 494 193 1485 1352 785 213 28