So a week or two ago they put new LED T-8 (4') bulbs overhead in my lab. Today I was doing some noise testing and I wondered how 'bad' the new bulbs were. They are great, a quick survey and I could see no peaks in my noise spectrum. So I grabbed a photodiode to look at them... The light is a beautiful 120 Hz signal.
When I looked close in (AC coupling, same gain for photodiode) there are 'steps' at ~50 kHz... but dang small.
Sweet! George H.