All wavelengths of light can be found in sunlight. Solar radiation has various diffusions and absorption is only possible with wavelengths from 300nm to 3.000nm.
Human eyes perceive 380-780nm wavelengths, and distinguish between light and color. The light of the green color (555nm) is detected more sensibly than the other colors.
Radiation effects to plants is physically effect radiation (300-800nm)and photosynthesis effect radiation(PAR : 400~700nm).
Those radiation absorb mid-blue colors and red colors, reflect green colors.
Plants do not use the green wavelength of light. Instead, they reflect the wavelength back, causing them to appear green in our eyes.
Blue
The blue light wavelength encourages the production of chlorophyll more than any other wavelength. This makes it essential for the production of strong, thick leaves and stems.
Red
When combined with the blue wavelength, the red wavelength stimulates flowering and fruiting and also plays a part in seed germination, as well as root, tuber and bulb development.
Other Factors
The light quantity and duration also can affect plant growth, as can other environmental factors such as temperature. Although incandescent lights can provide the red wavelength, they tend to create too much heat to use on plants.
What's spectrometer? Carlos testing LED growing lights with Public Laboratory Spectometer - Saro
Chemists use tools called spectrometers (there are several kinds) to analyze unknown solid or liquid samples. We are using it to identify frequencies of LED growing lights.
Spectrometers can also be used to identify species of plants or crop diseases, assess plumes from smokestacks, and have many other applications.
You can build your own spectrometer from Public Laboratory website
What's spectrometry?
What we perceive as a single color consists of multiple blended colors- just as green paint can be made from mixing yellow and blue paint. A spectrometer is a device that splits light into the various colors it is composed of, which we otherwise cannot distinguish with the naked eye. By viewing a substance through a spectrometer, one can distinguish the exact mixture of colors, which correspond to specific wavelengths of light, that make up the perceived color of the sample.
Spectrum test for LED growing light #1...
and #2.
Spectrum test comparison
As you can see has LED light #1 a difference in blue compared to LED light #2.
We found that the 440nm is more suitable for our plants.
Here's a comparison between 3 samples from the same company.