The lasers in your Blu-ray player emit at 405nm, which as the name suggests, is blue. Helium-neon lasers emit at 632.8nm, which is a bright red. However, a laser for example, emits only at a single very specific frequency. Sunlight appears white to us because it emits almost uniformly over all visible frequencies.
Higher frequency radiation, such as x-rays are absorbed by the atmosphere, as are lower frequencies, such as microwaves. The particular range of wavelengths coincides with a window in the Earth's atmosphere, through which this light can travel. Over the course of millions of years, the human eye has evolved to detect light in the range 380-780nm,Ī portion of the electromagnetic spectrum known as visible light, which we perceive as colour.
