Daylight includes visible light and invisible light. The visible light emitted by the sun includes a series of different colors of light, which contain different amounts of energy. Sunlight contains red, orange, yellow, green, cyan, blue, and purple light. The spectrum of these lights combines to produce what we call “white light” or sunlight.
There is an inverse relationship between the wavelength of light and the energy it contains. Light with relatively long wavelength contains less energy, while light with short wavelength has more energy. Light at the red end of the visible spectrum has a longer wavelength and therefore less energy. Light at the blue end of the spectrum has a shorter wavelength and more energy.
Electromagnetic rays beyond the red end of the visible spectrum are called infrared rays. They are warming but are not visible. At the other end of the visible spectrum, blue light with the shortest wavelength (and highest energy) is sometimes called blue-violet or violet light. This is why the invisible electromagnetic radiation that just exceeds the visible spectrum is called ultraviolet (UV). Ultraviolet rays have a higher energy than visible light, which allows them to produce suntan changes on the skin.
Blue light is generally defined as visible light in the range of 380 to 500 nm. Blue light is sometimes further broken down into blue-violet light (about 380 to 450 nm) and blue-green light (about 450 to 500 nm). Therefore, approximately one-third of all visible light is considered high-energy visible light (HEV) or “blue” light. Like ultraviolet radiation, visible blue light (the part of the visible light spectrum with the shortest wavelength and highest energy) has both benefits and dangers.
1. The source of blue light
Sunlight is the main source of blue light, and being outdoors during the day is where most of us are exposed to sunlight. However, there are many artificial indoor blue light sources, including fluorescent lights, LED lighting and flat-screen TVs. Most notably, the display screens of computers, electronic laptops, smart phones and other digital devices emit a lot of blue light.
2. The blue light makes the sky look blue.
When short-wave high-energy light on the blue end of the visible light spectrum strikes air and water molecules in the atmosphere, they are more easily scattered than other visible light. The high degree of scattering of these rays makes the cloudless sky look blue.
3. Blue light can reach the retina directly.
The anterior structure of the adult eye (cornea and lens) is very effective in preventing ultraviolet rays from reaching the photosensitive retina at the back of the eyeball. Even if you don’t wear sunglasses, less than one percent of the sun’s ultraviolet rays reach the retina. But almost all visible blue light passes through the cornea and lens and reaches the retina.
4. Blue light may increase the risk of macular degeneration.
The fact that blue light penetrates all the way to the retina (the inner layer behind the eye) is important because laboratory studies have shown that excessive exposure to blue light can damage the photoreceptor cells in the retina. This can cause changes similar to macular degeneration, which can lead to permanent vision loss. Although more research is needed to determine how much natural and artificial blue light is “too much” for the retina, many eye care service providers worry that the increased blue light exposure of computer screens, smartphones and other digital devices may increase by one. People are at risk of developing macular degeneration in later life.
5. Blue light can cause eye fatigue.
Since short-wave high-energy blue light is more easily scattered than other visible light, it is not easy to focus. When you look at computer screens and other digital devices that emit a lot of blue light, this unfocused visual “noise” reduces contrast and can cause digital eye strain. Studies have shown that lenses that block blue light (blue-violet light) with a wavelength of less than 450 nm can significantly improve contrast. Therefore, when you watch digital devices for a long time, computer glasses with yellow lenses may increase comfort.
6. After cataract surgery, blue light protection may be more important.
The lenses in the eyes of adults block nearly 100% of ultraviolet rays. As part of the normal aging process, the natural lens of the eye will eventually block some short-wavelength blue light, which is the blue light that is most likely to damage the retina and cause macular degeneration and vision loss. If you have cataracts and are about to undergo cataract surgery, you need to increase protection against blue light.
7. Blue light is also good for the body.
Some blue light exposure is essential for maintaining health. Studies have shown that high-energy visible light can increase alertness, help memory and cognitive function, and improve mood. In addition, blue light is also very important for regulating the circadian rhythm (the body’s natural wake and sleep cycle). Exposure to blue light during the day helps maintain a healthy circadian rhythm.
Post time: Jan-05-2021