Optical radiation and the light spectrum
Optical radiation is radiation that obeys the laws of geometric and wave optics. It covers the range of electromagnetic waves from 100nm to 1mm. It is divided into three ranges: ultraviolet, visible light and infrared. The visible range is from 380nm to 760nm.
Spectrum is an image obtained as a result of decomposing non-monochromatic light into components with different wavelengths:
Monochrome wave - one length
Spectrum - combination of monochromatic waves
UV spectrum (100-400nm) – The spectrum of UV light that is not visible to the human eye is outside the PAR range (100nm-400nm). About 10% of sunlight is ultraviolet radiation. Plants, like humans, can be damaged by overexposure to UV light. They are divided into 3 types: UV-A (315-400 nm), UV-B (280-315 nm) and UV-C (100-280 nm).
Blue spectrum (400-500nm) – Blue light is the main factor involved in photosynthesis. The blue light spectrum is largely responsible for improving plant quality – especially in deciduous crops. It promotes the opening of the stomatal apparatus – which allows more CO2 to enter the leaves. Blue light drives the peak absorption of the chlorophyll pigment, which is needed for photosynthesis.
This is essential for seedlings and young plants in the growing phase as they create a healthy root and stem structure – especially important when limiting stem stretching is essential.
Green spectrum (500-600nm) – Much of the green light that shines on the leaves is reflected. Thus, we see the green color of this plant. This would appear to be a waste of energy, but the reflected light is scattered and transferred to the lower leaves on the plant.
Red spectrum (600-700nm) – Red light is the second major factor involved in photosynthesis, but like blue light, it has exceptional results in plant physiology. It is responsible for lengthening the stems, determining the flowering period, budding and contributing to the circadian rhythm of plants.
Far red spectrum – far red – (700-800nm) – light that is not considered part of the PAR range (photosynthetic active radiation). When natural days are short, low-intensity (photoperiod) lighting is often provided to promote flowering of long-day plants. For some long-day plants, flowering is most accelerated when photoperiod lighting contains both red and far red light.