by Greg Green
Light can be separated into a spectrum, which form the colours of the rainbow. Red, Orange, Yellow, Green, Blue, Indigo, Violet. Each of these lights mix down to give white light. Artificial lights, because of their nature, tend to lean towards a tint of one of these colours when they mix down to form white light.
The electro-magnetic spectrum is a term used in lighting to describe the distribution of electro-magnetic radiation by reference to energy. This table roughly gives wavelengths, frequencies, and energies for parts of the spectrum. You may find it useful. Here is the visible part of the spectrum. Plants are green, which means that Plants absorb light at the middle of the spectrum (Orange to Indigo). Cannabis plants need this part of the light spectrum to reach full growing potential. The intensity of the light is also important. A light that feeds the full bandwidth with all light spectrums will work very well – like sunlight. When dealing with artificial lights it is better to choose a light that concentrates its intensity on the top part of the spectrum. The most common indoor light systems are called HID lights. We will discuss the full range of lights that you may come across in some grow rooms.