Electromagnetic (EM) Spectrum

https://scied.ucar.edu/learning-zone/earth-system/electromagnetic-spectrum Ask an optometrist: What’s the impact of blue light on vision? https://www.linkedin.com/pulse/ask-optometrist-whats-impact-blue-light-vision-lw3ge/ There’s a commonly held belief that blue light from digital devices damages your eyes. Here, an expert weighs in. Do a quick internet search, and you’ll probably turn up plenty of information stating that blue light from digital devices can hurt your vision—not to mention lead to other alarming effects like sleep disruption and even mental health changes. But there are several misconceptions about blue light, according to John Buch, a Senior Principal Research Optometrist at Johnson & Johnson. Primarily, there’s confusion about the main source of blue light. While people get up in arms about digital screens, “far and away, the most abundant and strongest source of natural blue-violet radiation is from the sun; so really, anytime you walk outside you’re being exposed to blue light,” Buch says. He explains that while computer screens, smartphones and televisions do emit blue light, the scale at which they do is vastly different from the sun. “Just 15 minutes of exposure to sunlight has been equated to 13 hours of nonstop looking at a computer screen. That said, it can’t be refuted that computer screens do emit the blue-violet end of the spectrum.” Setting industry standards: What is blue light? The electromagnetic spectrum includes a wide range of light, such as ultraviolet, gamma rays and X-rays. Humans can see a portion of the spectrum called visible light, ranging from violet light with a wavelength of 380 nanometers (nm) to blue, green, yellow, orange and red light measuring up to 780 nm. Within that visible spectrum, many people talk about high-energy visible (HEV) light, which is the blueish violet end of the spectrum, and has shorter wavelength and higher energy than other colors, Buch says. And within that HEV spectrum of 380-500 nm light, blue-violet light is an even narrower field, generally defined as light on the spectrum between 380-450 nm.