To the Editor.—
It is well known that the skin response to ultraviolet radiation in the sunburn range (280 to 320 nm) is dependent on the bandwidth of the incident radiation.1 The results presented here show the calculated variation of erythemal effectiveness with monochromator bandwidth for radiation beams of equal fluence, ie, the incident radiation energy per square centimeter (usually expressed as mJ · cm-2) is constant.In the determination of action spectra, a monochromator with equal entrance and exit slit widths is usually used. In a perfect monochromator, this arrangement gives a triangular distribution of intensity at the exit slit, with a maximum intensity at a central wavelength w0. The wavelengths present in the beam extend from w0—B to w0 + B, where B is termed the bandwidth and is equal to the width of the distribution at half the maximum intensity.2
Diffey BL. Variation of Erythema With Monochromator Bandwidth. Arch Dermatol. 1975;111(8):1070–1071. doi:10.1001/archderm.1975.01630200130020
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