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
Ultraviolet light therapy that tanning beds that primarily emit UVA cannot be effective for the treatment of psoriasis. Other limitations to the use of tanning beds for the treatment of skin conditions include the imprecise output of the lamps and beds, imprecise spectral targeting of commercial tanning beds, the fact that the patient or non-medical staff run the machines, and other acute or long-term side effects. Ultraviolet light therapy Ultraviolet light therapy or ultraviolet phototherapy is a form of treatment for certain skin disorders including atopic skin disorder and vitiligo when used with psoralen to form the PUVA treatment. It consists of irradiation