| Alan DeWeerd's Research | |
Quantum Optics | ||
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Surprisingly, it is sometimes possible to detect an object's presence without the absorption or scattering of a photon.
This phenomenon has been named interaction-free measurement. I've written an introduction to this subject. Publication: |
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Currently, I'm working on setting up quantum mechanical experiments with single photons. It will be possible to perform some of the
experiments described in the paper above. Related Links:
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Physics Education | ||
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There is an image between the lenses of a Keplerian (astronomical) telescope or
a compound microscope. We have developed a set of activities for liberal-arts physics courses
which are designed to demonstrate that to students.
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The images in various shapes of mirrors sometimes have the same handedness as the original object and
sometimes the handedness is changed. This is related to how many axes are inverted by the mirror.
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The cylindrical mirror has some interesting properties.
A point object reflected from one form not one point image, but two "line images." This
means the image is astigmatic.
When looking at the likenss of an object in a cylindrical mirror, inconsistent depth cues
may cause an observer to feel dizzy.
The cylindrical mirror can also be used to view anamorphic images.
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Reflections of parallel objects on the surface of a cup of tea have interesting
patterns. These depend on whether the surface is concave or convex.
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The helical mirror or "wind spinners" has become a common garden decoration.
These objects have some interesting optics.
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If you have a bumpersticker on your rear window, you will be able to read it in you rearview mirror.
This is an example of the longitudinal (front-back) inversion produced by a plane mirror.
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Describing the static equilibrium of a wine bottle balancing in a "wine butler" is an interesting challenge for students.
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Optical Tweezers | ||
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Optical tweezers use a focused laser beam to manipulated tiny objects under a microsope. They have numerous applictions in biophysics. A student and I have constructed an apparatus based on papers in AJP. As a test we moved around polystyrene spheres with radii of one micron to make a tiny "R" for Redlands. The height of the "R" is about 1/3 the thickness of a sheet of notebook paper. Related Links:
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Light Scattering &
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The wavelength dependence of light scattering is used to explain such phenomena as why the sky is blue and why sunsets are red. Angular dependence of scattering can be used to determine the size of spherical objects. We developed a way to measure the total scattering cross section for dielectric microspheres using an absorption spectrophotometer, an apparatus that many chemistry departments have. When the particles are very small compared to the wavelength of light, the process is well described by the Rayleigh approximation. When the particles are larger, the more complete Mie theory is required. We also performed Mie theory calculations related to atmospheric phenomena (the rainbow and the glory). The purpose was to study how these exact results are related to the predictions of geometrical optics by the localization principle. Publication: Related Links:
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