
208 Light Sources and Health
9.3 Flicker and Health Effects
Flicker is the modulation of a lamp’s light output mainly caused by uctuations
of the mains voltage supply. The mains frequency is 60 Hz in the United States
(50Hz in Europe) causing a icker at 120 Hz (100 Hz in Europe) in the lamp’s
output. Flicker is not perceptible at this frequency but it can still affect people.
All types of lamps suffer from icker (even LEDs that have a DC mode of opera-
tion) but people seemed to dislike, in particular, the icker of uorescent lamps
operated with magnetic ballasts at that mains frequency. It is not uncommon to
hear people in ofces comp ...