China's AC power is 50Hz, and the brightness of incandescent lamps changes 100 times per second. Lights that use AC directly are flashing. The incandescent lamp flashes at a frequency of 100 times per second, which is twice the grid frequency.
The human eye can perceive the change to within 30 Hz, and the light changes of 100 times per second (from dark to dark, then from dark to dark, ...) are not perceived by us, but studies have said that these changes Action) will have an effect on the human eye.
If strong light acts on the human eye, the pupil will contract in the eye; for weak light, the pupil will enlarge.
Therefore, the direct application of AC lights can cause damage to the eyes (referring to students who often use electric lights to read books). Some people invented the high-frequency lamp, which is tens of thousands of times per second. Because the human eye does not have time to change, it does not feel any change at all, so it can be said to be "unchanged" and achieve the purpose of eye protection. Turn ordinary 50Hz AC into high-frequency AC and use electronic frequency conversion. That is, in the high-frequency lamp, the actual 50Hz alternating current is first converted into high-frequency alternating current, and then the high-frequency alternating current is used for lighting.
However, the electromagnetic radiation of high-frequency electricity will also increase, that is, the electromagnetic radiation of the high-frequency lamp is larger than that of ordinary incandescent lamps and fluorescent lamps, and may cause another kind of damage. In addition, high frequency flash does not equal no flash.