The alternating current in China is 50 Hz, and the brightness of the incandescent lamp changes 100 times per second. Electric lamps that directly use alternating current all flicker. The flashing frequency of incandescent lamps is 100 times per second, which is twice the frequency of the power grid.
The sensory changes that the human eye can perceive are within 30 Hz, and the light changes 100 times per second (from light to dark, then from dark to light, ...) Although we will not perceive it, some studies say that these changes (flash (Motion) will have an effect on the human eye.
If strong light acts on the human eye, the pupil in the eye will contract; for weak light, the pupil will enlarge.
Therefore, an electric lamp directly applied with alternating current is harmful to the eyes (referring to students who often use electric lamps to read books). Someone invented the high-frequency lamp, which changes tens of thousands of times per second. Since the human eye has no time to change with it, it can't feel the change at all, so it can be said to be "unchanged" and achieve the purpose of eye protection. To convert ordinary 50Hz AC power into high-frequency AC power, use electronic frequency conversion. That is, in high-frequency lamps, the 50 Hz 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 high-frequency lamps is larger than that of ordinary incandescent lamps and fluorescent lamps, and it may also cause another kind of injury. In addition, high-frequency flashing does not mean not flashing.