# physconst

Physical constants

## Syntax

``const = physconst(name)``

## Description

example

````const = physconst(name)` returns the value of the physical constant `const` specified by the `name` argument.```

## Examples

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Determine the wavelength of a 1 GHz electromagnetic wave.

```freq = 1e9; lambda = physconst('LightSpeed')/freq```
```lambda = 0.2998 ```

Determine the thermal noise power per unit bandwidth in the in-phase (I) and quadrature (Q) channels of a receiver. Specify a receiver temperature of 290 K.

```T = 290; k = physconst('Boltzmann');```

Compute the noise power per unit bandwidth, split evenly between the I and Q channels. Units are in dB.

`Noise_power = 10*log10(k*T/2)`
```Noise_power = -206.9855 ```

## Input Arguments

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Name of physical constant, specified as `'Lightspeed'`, `'Boltzmann'`, or `'EarthRadius'`. See Physical Constants for a list of values for physical constants used in Phased Array System Toolbox™.

Example: `'Lightspeed'`

## Output Arguments

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Value of physical constant, returned as a real-valued scalar. All values are in SI units.

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### Physical Constants

This table lists the supported constants and their values in SI units.

ConstantDescriptionValue
`'LightSpeed'`Speed of light in vacuum299,792,458 m/s. Most commonly denoted by c.
`'Boltzmann'`Boltzmann constant relating kinetic energy to temperature$1.\text{3806504}×{10}^{-23}$ J/K. 2006 NIST value, most commonly denoted by k.
`'EarthRadius'`Mean radius of the Earth6,371,000 m

## Extended Capabilities

### External Websites

Introduced in R2011a