# User Guide

This document shows you how to use the program  MieCalc, if it is launched from a  HTML-document (i.e., from a web page). Note that some features of  MieCalc such as  storing output data in ASCII-format, printing the plots etc.  are only available in the stand alone  version of MieCalc

## Basics

MieCalc is a very flexible program to calculate the optical and electromagnetic scattering from a single homogeneous spherical particle illuminated by a plane incident light wave (Mie theory). With MieCalc, you can study the functional dependence of  light-scattering observables as functions of certain other parameters, for example:
• extinction cross-section cext as a function of  the particle diameter d
• scattered irradiance S11 as a function of the scattering angle theta
• degree of linear polarization P at a given scattering angle as a function of the particle radius r
• albedo A and  asymmetry factor g  as functions of the imaginary part of the refractive index of the particle
• scattering efficiency qsca as a function of the wavelength and the complex refractive index of the particle
• backscattering cross-section Cb as a function of the frequency of the incident radiation and the complex dielectric function of the particle.
• and almost any other combination of parameters

#### Input Parameters

All quantities required as input for calculations are called "input parameters".  MieCalc supports a large set of input parameters:
• the frequency, wavelength, inverse wavelength or wavenumber of the incident radiation
• the radius anddiameter of the particle
• the relative dielectric function (permittivity) or the refractive index  of the surrounding medium
• the complex relative dielectric function (permittivity) or the complex refractive index of the particle
• the scattering angle theta
Click here for a complete list of  parameters. Clearly, the set of input parameters is redundant: you can use the radius r  or the diameter d of the particle, or you may enter the frequency f, the wavelength lambda or the wavenumber k to specify the properties of the incident light.   With this redundance you can easily adjust MieCalc to your preferences.

There are three categories of input parameters:

1. Constants. These input parameters are kept at a fixed value during the calculation.
2. Variables.  A variable is specified by its range of variation and the number of data points to be evaluated. There must be at most one variable in a calculation. For instance, you can use the wavelength lambda,  the diameter d of the particle, the scattering angle theta, the refractive index of the surrounding medium refmed, etc. as the variable. Any input parameter can be used as a variable.
3. Tabulated parameters. These parameters are read in from the text area of the program in  ASCII format. There may be more than one tabulated parameter in a calculation, but you cannot use variables and tabulated parameters in the same calculation.

#### Output parameters

All quantities that can be plotted are called "output parameters". There are many output parameters supported by MieCalc:
• most input parameters can also be used as output parameters (typically, the abscissa of a plot is such a parameter).
• cross-sections for extinction, scattering, absorption, backscattering
• efficiencies for extinction, scattering, absorption, backscattering
• other integral scattering parameters such as albedo, asymmetry factor
• angular scattering observables: scattered intensity for various states of polarization, degree of linear polarization
Click here for a complete list of   parameters. In the calculations at least two output parameters must be specified, one of them playing the role of the abscissa, the others being plotted along the ordinate. For instance, you may specify the wavelength as the abscissa and the extinction, scattering, and absorption efficiencies Qext, Qsca, and Qabs  for the ordinate.

#### Consistent and Complete Set of Parameters

In order to perform a calculation you must specify the output parameters you are interested in and all  input parameters which are needed for the calculation. The program will check two things:
• Consistency of input parameters. Input parameters must be uniquely defined, there may be no ambiguities.  For example, you must not specify the radius r and the diameter d as input parameters, because the radius can be calculated from the diameter. Other "forbidden" combinations are
• frequency f and wavelength lambda, because one can calculate the free-space wavelength of light from its frequency
• dielectric function epsmed and refractive index refmed of surrounding medium, because the latter is the square root of the former.
• Completeness of input parameters. You must specify all input parameters needed to calculate the output parameters.
If the input parameters are inconsistent or not complete, the program issues a warning message and waits until acceptable input is entered. Only if  the input is OK are you able to run the program.