This interactive calculator simulates light scattering from spherical particles using Mie theory, allowing users to explore how changes in particle and optical properties influence scattering patterns. Calculations are performed using the miepython library [2].

Users can interactively adjust the following parameters using sliders or the input field:

• Particle radius (µm): Controls the size of the scattering particle.
• Wavelength (µm): Specifies the wavelength of the incident light.
• Refractive index (n): The real part of the particle's refractive index, which determines how strongly the particle refracts light.
• Absorption coefficient (k): The imaginary part of the refractive index, which represents absorption within the particle.
• Sigma (σ): The geometric standard deviation of the log-normal particle size distribution. A value of σ = 1 corresponds to a monodisperse (single-size) calculation, while larger values represent increasingly polydisperse particle populations.

To better represent real experimental samples, the program incorporates a log-normal particle size distribution when σ > 1, by averaging the scattering from 100 particle radii sampled from the distribution. This produces patterns that more closely resemble many experimental measurements of real particle ensembles [1].

Three interactive graphs are generated:

• Scattering Intensity vs. θ (Theta): Displays the normalized scattering intensity as a function of scattering angle from 0° to 180°. Separate curves are shown for parallel (SL), perpendicular (SR), and unpolarized (SU) scattered light.
• Scattering Intensity vs. q: Displays the same normalized scattering intensity as a function of the scattering vector q (cm^-1), which is commonly used when comparing scattering data collected at different wavelengths or particle sizes.
• Polar Scattering Pattern: Presents the angular scattering intensity in polar coordinates, providing a visual representation of the directional distribution of scattered light.

All calculated intensities are normalized to the forward-scattering intensity (θ = 0°), allowing scattering patterns obtained from different parameter values to be compared more easily. Interactive plots are calculated at 0.1° angular resolution, while exported data are generated at 0.01° angular resolution. This calculator is intended primarily as an educational and visualization tool, enabling students and researchers to develop an intuitive understanding of how particle size, optical properties, and size distributions influence Mie scattering.

The graphs include eight interactive controls:

• Download Plot: Saves the current graph view as an image.
• Zoom: Enables selecting and zooming into specific regions of the graph.
• Pan: Allows moving the graph view by dragging the plot area.
• Zoom In / Zoom Out: Adjusts the magnification level of the graph.
• Autoscale: Automatically adjusts the axes to display all available data within the view.
• Reset Axes: Returns the graph to its default view and axes settings.
• Legend Filtering: Clicking on legend labels toggles the visibility of the corresponding data series.

Additional navigation features are also available. The scroll wheel can be used to zoom in and out around the cursor position, double-clicking the graph restores the default zoom level, dragging the edges of the graph container to resize it, or view the graph in full-screen mode.

The polar graph provides a more limited set of controls and only supports Download as PNG and Zoom functionality.