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  2. Inverse-square law - Wikipedia

    en.wikipedia.org/wiki/Inverse-square_law

    The energy or intensity decreases (divided by 4) as the distance r is doubled; if measured in dB would decrease by 6.02 dB per doubling of distance. When referring to measurements of power quantities, a ratio can be expressed as a level in decibels by evaluating ten times the base-10 logarithm of the ratio of the measured quantity to the ...

  3. Radiant intensity - Wikipedia

    en.wikipedia.org/wiki/Radiant_intensity

    Radiant intensity is used to characterize the emission of radiation by an antenna: [2], = (), where E e is the irradiance of the antenna;; r is the distance from the antenna.; Unlike power density, radiant intensity does not depend on distance: because radiant intensity is defined as the power through a solid angle, the decreasing power density over distance due to the inverse-square law is ...

  4. Gaussian beam - Wikipedia

    en.wikipedia.org/wiki/Gaussian_beam

    At a distance from the waist equal to the Rayleigh range z R, the width w of the beam is √ 2 larger than it is at the focus where w = w 0, the beam waist. That also implies that the on-axis (r = 0) intensity there is one half of the peak intensity (at z = 0). That point along the beam also happens to be where the wavefront curvature (1/R) is ...

  5. Intensity (physics) - Wikipedia

    en.wikipedia.org/wiki/Intensity_(physics)

    In physics and many other areas of science and engineering the intensity or flux of radiant energy is the power transferred per unit area, where the area is measured on the plane perpendicular to the direction of propagation of the energy.

  6. Planck's law - Wikipedia

    en.wikipedia.org/wiki/Planck's_law

    The absorption coefficient α is the fractional change in the intensity of the light beam as it travels the distance ds, and has units of length −1. It is composed of two parts, the decrease due to absorption and the increase due to stimulated emission. Stimulated emission is emission by the material body which is caused by and is ...

  7. Black-body radiation - Wikipedia

    en.wikipedia.org/wiki/Black-body_radiation

    A graph of the spectral radiation intensity plotted versus frequency(or wavelength) ... On a side note, at a distance d, the intensity per area of ...

  8. Distance (graph theory) - Wikipedia

    en.wikipedia.org/wiki/Distance_(graph_theory)

    A metric space defined over a set of points in terms of distances in a graph defined over the set is called a graph metric. The vertex set (of an undirected graph) and the distance function form a metric space, if and only if the graph is connected. The eccentricity ϵ(v) of a vertex v is the greatest distance between v and any other vertex; in ...

  9. Laser beam profiler - Wikipedia

    en.wikipedia.org/wiki/Laser_beam_profiler

    Beam divergence: This is a measure of the spreading of the beam with distance. Beam profile: A beam profile is the 2D intensity plot of a beam at a given location along the beam path. A Gaussian or flat-top profile is often desired. The beam profile indicates nuisance high-order spatial modes in a laser cavity as well as hot spots in the beam.