Relativistic Doppler effect invisible ultraviolet wavelengths, infrared light is blueshifted into the visible range. Precisely what changes in the colors one sees depends on the physiology of the human eye and on the spectral characteristics of the light sources being observed. The Doppler effect (with arbitrary direction) also modifies the perceived source intensity: this can be expressed concisely by the fact that source strength divided by the cube of the frequency is a Lorentz invariant This implies that the total radiant intensity (summing over all frequencies) is multiplied by the fourth power of the Doppler factor for frequency. As a consequence, since Planck's
UV marker emits visible light and make the message readable for human eyes. Fluoresce is caused by a conversion of energy; when the invisible ultraviolet falls on the fluorescent surface, it is absorbed and re-emitted as visible light radiation. The absorption of energy by the electrons in the UV-visible ink enables this to happen. When an extra amount of energy is absorbed, the electrons jump into higher energy orbital patterns surrounding the nucleus. Eventually, the energy is released as visible light when they fall back to their normal orbital shell. The difference between the original electron orbital and the new orbital pattern