In the observations at 4.3 mm ( Coates, 1959 ), the diameter of the antenna beam, 6'.7, was small enough to allow resolution of some of the larger features of the lunar surface, and contour diagrams have been made of the lunar brightness distribution at three lunar phases.

Very recently, observations have been made at 8-mm wave length with a reflector 22 meters in diameter with a resultant beam width of only about 2' ( Amenitskii, Noskova, and Salomonovich, 1960 ).

The half-intensity diameter of the antenna beam was about 9', and the angle subtended by the moon included the entire main beam and part of the first side lobes.

The half-intensity diameter of the main lobe of the antenna was about 18'.5, and the brightness temperature was reduced by assuming a Gaussian shape for the antenna beam and a uniformly bright disk for the moon.

and the magnification of beam diameter at the interface, m,

The beam in the cavity and the output beam of the laser, when travelling in free space ( or a homogenous medium ) rather than waveguides ( as in an optical fiber laser ), can be approximated as a Gaussian beam in most lasers ; such beams exhibit the minimum divergence for a given diameter.

The beam of a single transverse mode ( gaussian beam ) laser eventually diverges at an angle which varies inversely with the beam diameter, as required by diffraction theory.

The electron beam can focused to a spot approximately 1 nanometer in diameter, and microscopes are able to resolve details ranging from 1 – 20 nm in size.

The electron beam, which typically has an energy ranging from 0. 2 keV to 40 keV, is focused by one or two condenser lenses to a spot about 0. 4 nm to 5 nm in diameter.

Provided the electron gun can generate a beam with sufficiently small diameter, a SEM could in principle work entirely without condenser or objective lenses, although it might not be very versatile or achieve very high resolution.

The beam has to have a large diameter so that only a small portion of the beam misses the sail due to diffraction and the laser or microwave antenna has to have a good pointing stability so that the craft can tilt its sails fast enough to follow the center of the beam.

A small pellet of fusion fuel ( with a diameter of a couple of millimeters ) would be ignited by an electron beam or a laser.

Under the Monorail Society beam width criteria, some but not all maglev systems are considered monorails, such as the Transrapid and Linimo.

In the analysis of the single slit, the non-zero width of the slit is taken into account, and each point in the aperture is taken as the source of one contribution to the beam of light ( Huygen's wavelets ).

Five definitions of the beam width are in common use: D4σ, 10 / 90 or 20 / 80 knife-edge, 1 / e < sup > 2 </ sup >, FWHM, and D86.

The beam width can be measured in units of length at a particular plane perpendicular to the beam axis, but it can also refer to the angular width, which is the angle subtended by the beam at the source.

The term " beam width " may be preferred in applications where the beam does not have circular symmetry.

The simplest way to define the width of a beam is to choose two diametrically opposite points at which the irradiance is a specified fraction of the beam's peak irradiance, and take the distance between them as a measure of the beam's width.

An obvious choice for this fraction is ½ (− 3 dB ), in which case the diameter obtained is the full width of the beam at half its maximum intensity ( FWHM ).

This is also called the half-power beam width ( HPBW ).

For multimodal marginal distributions ( a beam profile with multiple peaks ), the 1 / e < sup > 2 </ sup > width usually does not yield a meaningful value and can grossly underestimate the inherent width of the beam.

For an ideal single-mode Gaussian beam, the D4σ, D86 and 1 / e < sup > 2 </ sup > width measurements would give the same value.

Although X-rays are most commonly used, the beam is not always electromagnetic radiation.

The electron microscope uses electrostatic and electromagnetic " lenses " to control the electron beam and focus it to form an image.

The electron beam is accelerated by an anode typically at + 100 keV ( 40 to 400 keV ) with respect to the cathode, focused by electrostatic and electromagnetic lenses, and transmitted through the specimen that is in part transparent to electrons and in part scatters them out of the beam.

The best-known instance is the parabolic reflector, which is a mirror or similar reflective device that concentrates light or other forms of electromagnetic radiation to a common focal point, or conversely, collimates light from a point source at the focus into a parallel beam.

The energy exchange between the electron beam and the sample results in the reflection of high-energy electrons by elastic scattering, emission of secondary electrons by inelastic scattering and the emission of electromagnetic radiation, each of which can be detected by specialized detectors.

Like all electromagnetic radiation, the properties of X-rays ( or gamma rays ) depend only on their wavelength and polarization ( or, in a polychromatic beam, the distributions of wavelength and polarization ).

Beam diameter is usually used to characterize electromagnetic beams in the optical regime, and occasionally in the microwave regime, that is, cases in which the aperture from which the beam emerges is very large with respect to the wavelength.

The beam divergence of an electromagnetic beam is an angular measure of the increase in beam diameter or radius with distance from the optical aperture or antenna aperture from which the electromagnetic beam emerges.

Beam divergence is often used to characterize electromagnetic beams in the optical regime, for cases in which the aperture from which the beam emerges is very large with respect to the wavelength.

For an electromagnetic wave, the coherence time is the time over which a propagating wave ( especially a laser or maser beam ) may be considered coherent.

In telecommunication and astronomy, forward scatter is the deflection — by diffraction, nonhomogeneous refraction, or nonspecular reflection by particulate matter of dimensions that are large with respect to the wavelength in question but small with respect to the beam diameter — of a portion of an incident electromagnetic wave, in such a manner that the energy so deflected propagates in a direction that is within 90 ° of the direction of propagation of the incident wave ( i. e., the phase angle is greater than 90 °).

In optics, a Gaussian beam is a beam of electromagnetic radiation whose transverse electric field and intensity ( irradiance ) distributions are well approximated by Gaussian functions.

DeKalb budget shows county is on beam

At the entrance side of the shelter, each roof beam is rested on the inside 4 inches of the block wall.

Hotei is 23 feet long with an 8-1/2-foot beam and every inch a family boat.

The frequency used for these experiments is 15 mc. and the transducer is a specially cut crystal with an epoxy lens capable of providing beam diameters smaller than one millimeter.

The transducer itself moves the beam in a sector scan, just like a radar antenna, while the entire transducer structure is moved over a 90-degree arc in front of the eye to `` look into '' all corners.

The ratio of the measured antenna temperature change during a drift scan across the moon to the average brightness temperature of the moon over the antenna beam ( assuming that the brightness temperature of the sky is negligible ) was found, by graphical integration of the antenna directivity diagram, to be 0.85.

The measured brightness temperature is a good approximation to the brightness temperature at the center of the lunar disk because of the narrow antenna beam and because the temperature distribution over the central portion of the moon's disk is nearly uniform.

The sighting procedure includes the use of a fixture for the transit to project a beam of light, which is darkened by crossed hairs, on the accelerometer mirror.

As this direction is random, the beam could be expected to spread into a line.

The device uses a magnet to bend the trajectory of a beam of ions, and the amount of deflection is determined by the ratio of an atom's mass to its charge.

Synthetic amethyst is produced by gamma-ray, x-ray or electron beam irradiation of clear quartz which has been first doped with ferric impurities.

At the end of each line the beam returns to the start of the next line ; the end of the last line is a link that returns to the top of the screen.

As it passes each point the intensity of the beam is varied, varying the luminance of that point.

The test is unstable ( i. e. the crack propagates along the entire specimen once a critical load is attained ) and a modified version of this test characterised by a non constant inertia was proposed called the tapered double cantilever beam ( TDCB ) specimen.

At the instant of any observation of an object, the apparent position of the object is displaced from its true position by an amount which depends solely upon the transverse component of the velocity of the observer, with respect to the vector of the incoming beam of light ( i. e., the line actually taken by the light on its path to the observer ).

Another way to state this is that the emitting object may have a transverse velocity with respect to the observer, but any light beam emitted from it which reaches the observer, cannot, for it must have been previously emitted in such a direction that its transverse component has been " corrected " for.

For the simple case where the direction of the light beam along the line SE is perpendicular to the motion of the observer then only light emitted at an angle equal to the arc cosine of the ratio of the observer's speed to the speed of light will reach the telescope.

According to the special theory of relativity, the aberration looks as a transform of the celestial sphere due to different frames of reference and is virtually a special case of velocity addition, namely one of the light beam and frames ' relative velocity v. The formula from relativistic aberration can be simplified to

Laser Doppler anemometers use a beam of light from a laser that is divided into two beams, with one propagated out of the anemometer.

Particulates ( or deliberately introduced seed material ) flowing along with air molecules near where the beam exits reflect, or backscatter, the light back into a detector, where it is measured relative to the original laser beam.

The vertical force on the bridge becomes a shear and flexural load on the beam which is transferred down its length to the substructures on either side They are typically made of steel, concrete or wood.