It simulates how the light's wavelength and frequency changes because of the black hole and shows the way it changes color. Near the black hole, the light's wavelength becomes shorter like the blue shift in the galaxy due to gravity, and light's blue shift occurs.

The point in the center of the circle indicates a black hole with a radius of 1(rg). The blue circles around it indicate from the inner circle as 2,3,4,5...(rg).

Firstly, set the wavelength when the light reached infinite space. Then choose the firing place of light from the units of rg. By calculation, the light's locus will be drawn with color and wavelength under those conditions. Also the wavelength at the firing place will be shown. Red shift occurrs as it goes farther from black hole because wavelength stretches. A most favorable starting point will be around 4000ang.

You can not see ultraviolet and infrared, but in this simulation, they will be shown with these colors below.