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RC time constant. The RC time constant, denoted τ (lowercase tau ), the time constant (in seconds) of a resistor–capacitor circuit (RC circuit), is equal to the product of the circuit resistance (in ohms) and the circuit capacitance (in farads ): It is the time required to charge the capacitor, through the resistor, from an initial charge ...
Time constant. In physics and engineering, the time constant, usually denoted by the Greek letter τ (tau), is the parameter characterizing the response to a step input of a first-order, linear time-invariant (LTI) system. [1] [note 1] The time constant is the main characteristic unit of a first-order LTI system. It gives speed of the response.
Snell's law. Refraction of light at the interface between two media of different refractive indices, with n 2 > n 1. Since the velocity is lower in the second medium (v 2 < v 1 ), the angle of refraction θ 2 is less than the angle of incidence θ 1; that is, the ray in the higher-index medium is closer to the normal.
186 282 mi. The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. It is defined as the distance that light travels in free space in one second, and is equal to exactly 299 792 458 m (approximately 983 571 055 ft or 186 282 mi ). Just as the second forms the basis for other units of time, the ...
In special relativity, a light cone (or null cone) is the surface describing the temporal evolution of a flash of light in Minkowski spacetime. This can be visualized in 3-space if the two horizontal axes are chosen to be spatial dimensions, while the vertical axis is time. [3] The light cone is constructed as follows.
The speed of light in vacuum, commonly denoted c, is a universal physical constant that is exactly equal to 299,792,458 metres per second (approximately 300,000 kilometres per second; 186,000 miles per second; 671 million miles per hour). [Note 3] According to the special theory of relativity, c is the upper limit for the speed at which ...
In physics, the term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. [ 4][ 5] In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum, and polarization.
In physics, time is defined by its measurement: time is what a clock reads. [1] In classical, non-relativistic physics, it is a scalar quantity (often denoted by the symbol ) and, like length, mass, and charge, is usually described as a fundamental quantity.