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Northern Hemisphere circumpolar stars around Polaris, with a long-exposure producing a star trail photo. A pole star is a visible star that is approximately aligned with the axis of rotation of an astronomical body; that is, a star whose apparent position is close to one of the celestial poles.
A diagram of the electromagnetic spectrum, showing various properties across the range of frequencies and wavelengths. The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength.
Asymmetry is the absence of, or a violation of, symmetry (the property of an object being invariant to a transformation, such as reflection). [1] Symmetry is an important property of both physical and abstract systems and it may be displayed in precise terms or in more aesthetic terms. [2]
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Coherence expresses the potential for two waves to interfere.Two monochromatic beams from a single source always interfere. [1]: 286 Wave sources are not strictly monochromatic: they may be partly coherent.
The Gaussian function has a 1/e 2 diameter (2w as used in the text) about 1.7 times the FWHM.. At a position z along the beam (measured from the focus), the spot size parameter w is given by a hyperbolic relation: [1] = + (), where [1] = is called the Rayleigh range as further discussed below, and is the refractive index of the medium.
True color image of the Trifid Nebula, showing complex gas and plasma structure. A nebula (Latin for 'cloud, fog'; [1] pl.: nebulae, or nebulas [2] [3] [4] [5]) is a ...
Planck's law accurately describes black-body radiation. Shown here are a family of curves for different temperatures. The classical (black) curve diverges from observed intensity at high frequencies (short wavelengths).