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Integration of an absorption coefficient over a path from s 1 and s 2 affords the optical thickness (τ) of that path, a dimensionless quantity that is used in some variants of the Schwarzschild equation. When emission is ignored, the incoming radiation is reduced by a factor for 1/e when transmitted over a path with an optical thickness of 1.
The most general form of Cauchy's equation is = + + +,where n is the refractive index, λ is the wavelength, A, B, C, etc., are coefficients that can be determined for a material by fitting the equation to measured refractive indices at known wavelengths.
The time constant is related to the RC circuit's cutoff frequency f c, by = = or, equivalently, = = where resistance in ohms and capacitance in farads yields the time constant in seconds or the cutoff frequency in hertz (Hz).
In condensed matter physics, relaxation is usually studied as a linear response to a small external perturbation. Since the underlying microscopic processes are active even in the absence of external perturbations, one can also study "relaxation in equilibrium" instead of the usual "relaxation into equilibrium" (see fluctuation-dissipation theorem).
First order LTI systems are characterized by the differential equation + = where τ represents the exponential decay constant and V is a function of time t = (). The right-hand side is the forcing function f(t) describing an external driving function of time, which can be regarded as the system input, to which V(t) is the response, or system output.
The concept was first introduced by S. Pancharatnam [1] as geometric phase and later elaborately explained and popularized by Michael Berry in a paper published in 1984 [2] emphasizing how geometric phases provide a powerful unifying concept in several branches of classical and quantum physics.
The voltage (v) on the capacitor (C) changes with time as the capacitor is charged or discharged via the resistor (R) In electronics, when a capacitor is charged or discharged via a resistor, the voltage on the capacitor follows the above formula, with the half time approximately equal to 0.69 times the time constant, which is equal to the product of the resistance and the capacitance.
The planar, parallel-source-rays case: suppose the direction vector is (,) and the mirror curve is parametrised as ((), ()). The normal vector at a point is ( − v ′ ( t ) , u ′ ( t ) ) {\displaystyle (-v'(t),u'(t))} ; the reflection of the direction vector is (normal needs special normalization)