top of page
Light and the Eye
The retina has two different types of cells that detect light, rods and cones. These are cells that are sensitive to light and called photoreceptors. Rods are activated when you’re in low or dim light. Cones are stimulated in brighter areas. Most of us have about 6 million cones and 110 million rods. Cones contain photopigments or color-detecting molecules. Humans typically have three types of photo pigments red, green and blue. Each type of cone is sensitive to different wavelengths of visible light. In the daytime, a lemon’s reflected light activates both red and green cones. The cones then send a signal along the optic nerve to the visual cortex of the brain. The brain processes the number of cones that were activated and the strength of their signal. After the nerve impulses are processed, you see a color— in this case, yellow.
Electromagnetic Spectrum
White-Blue LED’s happen to fall between 440 - 490 nm, having shorter wavelengths/more energy than most other colors. This abundance of energy that blue light has causes more of a strain on the eye than colors like yellow or orange.
Helmholtz-Kohlrausch (HK) Effect
The HK effect describes how the same light can appear light or dark depending on what surrounds it. If a blue-white light were to be shone in an already bright area, then it wouldn’t cause so much of a strain on the eyes. If the same light were placed in a dark room, it would be much harder to look at. The HK effect also states that the color of a light can also affect its perceived brightness. This goes more with the psychological aspect, because the brightness of each color, depends on the person.
​
​
​
bottom of page