We all use technology every day. Smartwatches, smartphones and tablet devices make computers convenient and fun. But have any adults told you not to spend so much time on these devices? One downside of staring at a screen so much is the danger to your eyes. It’s because of the color of light coming out of the screen.
Scientists the world over are discovering the dangers of blue light coming from smartphones, tablets and other devices. Researchers at the University of Toledo in the US have found that staring at a screen can irreparably damage our eyes over time. It happens slowly, but damage builds up over time in the cells of the eye that are sensitive to light. However, not all blue light sources are the same.
Light from the sun contains all the colors that we can see: red, orange, yellow, green, blue, violet and shades in between. When all of these wavelengths of light combine, we only see “white light” or sunlight. Although the blue and violet wavelengths have more energy than the others, the sun’s blue light is balanced with the other wavelengths.
Man-made light sources also contain many wavelengths. LED lighting, fluorescent bulbs and flat-screen televisions all give off blue light. The problem is out of all the visible light from man-made devices, roughly one-third of it is considered “blue” or high-energy visible (HEV) light. That light is far more concentrated than the sun’s blue light which gets scattered in the atmosphere. The amount of HEV light given off by man-made devices is very small when compared with the amount given off by the sun. But while very few people would spend hours staring at the sun, many of us spend as much time staring at our devices. Just two hours can give you eyestrain.
人造光源跟太陽光一樣，也含許多不同波長。LED 燈、日光燈泡和平板電視都會發出藍光。人造光源器材最大的問題是，它們發出的可見光中，近約3 分之1 被視為藍光或高能可見光。跟分布在大氣層裡的太陽藍光相較，人造藍光的能量更加集中。人造器材或載具發出高能可見光的量，自然無法跟太陽相比。花數小時直視太陽的人少之又少，但花數小時直視載具的人卻不少。只需盯著螢幕兩小時，眼睛就受不了。
Should we hide from all blue light? Definitely not! The sun’s blue light sets your circadian rhythm—we need that to get a good night’s sleep. In countries that experience long, dark winters, it’s easy for people to get too little blue light. This leads to seasonal affective disorder (SAD) in which people feel depressed. Blue light makes us feel more alert and helps us to remember things more clearly.