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Lunar Laser Ranging experiments. Lunar Laser Ranging (LLR) is the practice of measuring the distance between the surfaces of the Earth and the Moon using laser ranging. The distance can be calculated from the round-trip time of laser light pulses travelling at the speed of light, which are reflected back to Earth by the Moon's surface or by one ...
Retroreflectors are devices which reflect light back to its source. Six were left at six sites on the Moon by three crews of the Apollo program, two by remote landers of the Lunokhod program, and one by the Chandrayaan program. [1] Lunar reflectors have enabled precise measurement of the Earth–Moon distance since 1969 using lunar laser ranging.
A waveplate mounted in a rotary mount. A waveplate works by shifting the phase between two perpendicular polarization components of the light wave. A typical waveplate is simply a birefringent crystal with a carefully chosen orientation and thickness. The crystal is cut into a plate, with the orientation of the cut chosen so that the optic axis ...
For a stack of plates, each reflection depletes the incident beam of s-polarized light, leaving a greater fraction of p-polarized light in the transmitted beam at each stage. For visible light in air and typical glass, Brewster's angle is about 57°, and about 16% of the s -polarized light present in the beam is reflected for each air-to-glass ...
A scanning mirror with which the light is deflected is attached to a rotating shaft. The entire disc or oblong sheet to be read is illuminated by a large playback light source at the back of the transparent plate instead by focused laser light in reflective mode. There is no objective lens for reading the data.
The word laser is an anacronym that originated as an acronym for light amplification by stimulated emission of radiation. [ 1 ][ 2 ] The first laser was built in 1960 by Theodore Maiman at Hughes Research Laboratories, based on theoretical work by Charles H. Townes and Arthur Leonard Schawlow.
A common-path interferometer is a class of interferometers in which the reference beam and sample beams travel along the same path. Examples include the Sagnac interferometer, Zernike phase-contrast interferometer, and the point diffraction interferometer. A common-path interferometer is generally more robust to environmental vibrations than a ...
A zone plate is a device used to focus light or other things exhibiting wave character. [1] Unlike lenses or curved mirrors , zone plates use diffraction instead of refraction or reflection . Based on analysis by French physicist Augustin-Jean Fresnel , they are sometimes called Fresnel zone plates in his honor.