Everyday Science, Everyday stuff

Why Are Blue Lights Harder to See?

blue snow?” (CC BY-SA 2.0) by [cipher]
You must have noticed that blue Christmas fairy lights seem blurry as compared to red and green ones. We find it difficult to read blue neon signs while we can read red and green signs with ease. In order to understand this phenomena we need to understand the physics behind it.

Different rays of light have different wavelengths. Human eye responds to wavelengths from about 390 to 700 nm(nanometer). Blue light has a shorter wavelength and is generally defined as visible light ranging from about 390 to 500 nm. Red and green light rays have a longer wavelength.  

The wavelength of the light rays is inversely proportional to the amount of energy they contain. Light rays that have long wavelengths contain less energy while those with short wavelengths have more energy. Thus blue light contain more energy as compared to red and green rays.

blue illumination” (CC BY 2.0) by saotin

The short wavelength, high energy blue light is scattered more easily than other visible light.  Thus when blue light enters our eye, it is focused over a larger area of our retina as compared to red and green light. We are hence unable to view blue light easily and it appears blurry. Computer screens, smartphones and other digital devices emit significant amounts of blue light. Research indicates that overexposure to such electronic devices may prove harmful to our eye.


References
  1. http://www.allaboutvision.com/cvs/blue-light.htm
  2. http://www.bluelightexposed.com/#what-is-bue-light
  3. http://techreport.com/news/8372/blue-leds-actually-more-blinding
  4. http://www.assemblymag.com/articles/91320-beware-the-blue-light