Junk light refers to artificial light sources – such as LEDs, compact fluorescent (CFLs), or any device with an LED screen (computers, smartphones, tablets, and laptops). These light sources amplify the blue, green and purple parts of the light spectrum. Your body’s natural sleep-wake cycle, also known at your circadian rhythm, is incredibly sensitive to these particular wavelengths. When exposed to any of them at the wrong time of day or night, you end up with junk light, which can directly impact your sleep, mood, focus, and cognitive function.