You see, humans(and all mammals in general) have somewhat of a clock on how they wake. It happens throughout the body, but the master clock that syncs the rest would be the suprachiasmatic nucleus(SCN), as small part of the brain located in the hippocampus. However, the biological clock adjust itself based around certain types of light that are absorbed within the retina using a special photo receptor in the back of the eye. Cells called intrinsically photosensitive retinal ganglion cells(or ipRGC) determine what time of day is in dependence on the light presented to the eye. This then activates the pineal gland releases melatonin(sleep drug) and our body temperature to change depending on what the ipRGC states. Of course, the drug isn’t constantly produced throughout a 24hr day, and is maximized in deep sleep just three hours before you wake up. The same could be said with the body temperature, as it’s at its lowest. This is extremely important because blue light(represent to our bodies daylight) has been considered to naturally restore our biological clock as it should. Meanwhile, red light (sunset) influences our body the most when going to sleep by the highest amount of melatonin. Certain other lights create different effects, but blue and red are the most power successors as they rival each other in the light spectrum for Kelvin. Underneath is the spectrum sensitivity for photo receptors and where it scales in nanometers. Photopigment Melanopsin(light-sensitive retinal proteins that are within ipRGC and effect the entire process) are most sensitive between the nanometers of 450 to 480.
Helmut Sachs “Light Spectrum” remembereverything.org Remember Everything You Want…., Web, Feb 19, 2018. Nov 29, 2018