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Differences In The Spectral Output Of Single- And Double-Ended High-Pressure-Sodium Lamps, Jun Liu, Bruce Bugbee

Photobiology

High pressure sodium lamps have a low fraction of blue photons, and this fraction is reduced from 3.6% to 2.6% in the newer style double-ended bulbs. About half of the photons in the “blue” region (400 to 499 nm) are between 491 and 499 nm. These photons have low biological activity for cryptochrome activation.