# Medium¶

Contains

• Medium

class sympy.physics.optics.medium.Medium(name, permittivity=None, permeability=None, n=None)[source]

This class represents an optical medium. The prime reason to implement this is to facilitate refraction, Fermat’s principle, etc.

Parameters

name: string

The display name of the Medium.

permittivity: Sympifyable

Electric permittivity of the space.

permeability: Sympifyable

Magnetic permeability of the space.

n: Sympifyable

Index of refraction of the medium.

Explanation

An optical medium is a material through which electromagnetic waves propagate. The permittivity and permeability of the medium define how electromagnetic waves propagate in it.

Examples

```>>> from sympy.abc import epsilon, mu
>>> from sympy.physics.optics import Medium
>>> m1 = Medium('m1')
>>> m2 = Medium('m2', epsilon, mu)
>>> m1.intrinsic_impedance
149896229*pi*kilogram*meter**2/(1250000*ampere**2*second**3)
>>> m2.refractive_index
299792458*meter*sqrt(epsilon*mu)/second
```

References

R658

https://en.wikipedia.org/wiki/Optical_medium

property refractive_index

Returns refractive index of the medium.

Examples

```>>> from sympy.physics.optics import Medium
>>> m = Medium('m')
>>> m.refractive_index
1
```
property speed

Returns speed of the electromagnetic wave travelling in the medium.

Examples

```>>> from sympy.physics.optics import Medium
>>> m = Medium('m')
>>> m.speed
299792458*meter/second
>>> m2 = Medium('m2', n=1)
>>> m.speed == m2.speed
True
```