Many people often spend hours watching videos on their phones before sleep, with the lights off. However, did you know that using your phone in the dark is not a very good idea?The screen of your phone sends out blue light, which is quite harmful to your eyes. It can also be hard for you to go asleep.
What is blue light?Blue light is everywhere. It is sent out both by artificial （人造的） light and by our biggest light—the sun! Blue light is the part of visible light which has the second shortest wavelength. Light with shorter wavelengths have greater power. The strong energy of blue light allows it to pass easily through the cornea （角膜） of our eyes. Therefore, blue light is quite harmful to our eyes.
However, blue light isn't all that bad. After all, it is a part of sunlight. In fact, it can help to improve our sleep. The problem, however, lies in the bright screen lights we stare at each night. In other words, the problem isn't exactly the exposure （暴露） to blue light, but the timing of our exposure to it.
Some scientists studied the difference between reading a paper book and an e﹣book before bedtime. They found that it took longer for people who used an e﹣reader to fall asleep. These people were also less smart in the following morning.
So, to protect the quality of your sleep, avoid screens an hour or two before your bedtime. If you must use your phone before going to bed, keep a night lamp on.
