# Documentation

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# physconst

Physical constants

## Syntax

Const = physconst(Name)

## Description

Const = physconst(Name) returns the constant specified in the Name argument. Valid values are 'LightSpeed', 'Boltzmann', or 'EarthRadius'. Values are in SI units.

## Input Arguments

 Name Character vector that indicates which physical constant the function returns. Values are not case sensitive.

## Output Arguments

 Const Value of physical constant specified in the input argument Name.

## Examples

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Determine the wavelength of a 1 Ghz electromagnetic wave.

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

Approximate the thermal noise power per unit bandwidth in the I and Q channels of a receiver.

Specify the receiver temperature and Boltzmann constant.

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

Compute the noise power per unit bandwidth, split evenly between the in-phase and quadrature channels.

Noise_power = 10*log10(k*T/2);

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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 energy to temperature$1.38×{10}^{-23}$ J/K. Most commonly denoted by k.