PHGN-398A Fall
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Revision as of 17:41, 19 September 2010
| Main Page | > | Physics Course Wikis |
Course Information
Instructors: Vince Kuo, Patrick Kohl and Frank Kowalski
Course Links
Creativity in Science and Engineering
PROBLEM 1: Measuring the wavelength of an unknown laser: What apparatus would you use to measure the wavelength of an unknown laser using a He-Ne laser whose wavelength is know to 8 significant figures?
Green Hat comments
Apparatus:
-two slit interferometer -Superimpose the two laser beams with a beam splitter. Look at the time dependent detector output for beats and take a Fourier transform.
-Superimpose the two laser beams with a beam splitter then shine them on a grating. Look at the spatial separation.
-Superimpose the two laser beams in a Michelson interferometer. Then measure constructive interference of each color and compare.
-Superimpose the two beams and shine them into a parallel plate device (Fabrey-Perot) interferometer. Vary the plate spacing and compare the maxims observed.
-Shine the two beams in a "funnel" absorbing chamber and look for where each is extinguished.
-Cross the two beams at a known angle and look for the spacing of the fringes.
-Measure the combined color of the two beams together.
-Measure standing waves in a cavity whose size is changed.
-Use a dielectric material with a known index of refraction to measure cause a know phase shift and measure its effects.
-Look at the diffraction pattern as both beams traverse a single slit interferometer.
combing ideas comments
questioning comments
analogy comments
reminding comments
anomaly comments
White Hat comments
Descriptions of grating spectrometer are found at these two links:
The resolution of a grating spectrometer, or the smallest change in wavelength measurable divided by the wavelength is the order number times the number of grooves illuminated, which is about 1 part in 2 for a double slit "grating" and about 1 part in 10,000 for an expensive spectrometer. This is discussed in the following link:
A Michelson or Fabry-Perot interferometer has a change of a fringe every time one mirror is moved half a wavelength. For a mirror motion of 1 meter the number of fringes for the He-Ne laser (wavelength of 6328 Angstroms) is 1.58 million fringes. How many fringes for the unknown laser if both beams were superimposed? How does this resolution compare with the grating spectrometer?
Black Hat comments
Yellow Hat comments
Red Hat comments
Blue Hat comments
Problem 2: Measuring the Mass Extracted from a Quarry
Green Hat comments
-measure the weight of the trucks carrying the material out of the quarry.
-measure the effect of mass loss on the gravitational attraction.
-measure the volume extracted and determine the mass from its density.
-measure the flow rate of material on a conveyor belt.
-use fuel consumption in the trucks to measure energy required to move the mass.
-measure the mass as it is loaded on the truck via a scale on the scooper truck.
-use Archimedes principle to measure displacement and therefore volume. Density gives mass.
