2/29/2024 0 Comments Light intensity equationBy measuring the scattering intensity for many samples of various concentrations, the second virial coefficient, A 2, can be calculated. Measurement of the scattering intensity at many angles allows calculation of the root mean square radius, also called the radius of gyration R g. The correct conversion factor to get PPFD from Joules/m 2 /s will be 4.6.Static light scattering is a technique in physical chemistry that measures the intensity of the scattered light to obtain the average molecular weight M w of a macromolecule like a polymer or a protein in solution. Following our example working in a greenhouse environment with natural light. In order to convert energy units to □mol/ m 2/s we need to multiply energy units by the corresponding conversion factor. Below you will find a useful table sharing conversion factors for different light sources. Different light colors will have a different conversion factor. When working with LED lighting, light quality needs also to be considered in light conversions. The conversion factor will totally depend on the source of light. In order to convert energy units to □mol/ m 2/s light source must be considered. Last step will be to make conversion from energy units to the unit used to understand light in plants: PPFD.At this point we have a close number for the light present inside the greenhouse in energy units (Joules/m 2/s or W/m 2.). The next step then will be to obtain the 70% of the total light calculated on the previous step. We can assume a 70% of light can be transmitted from outside to inside our greenhouse. Greenhouse structure and coverings reduce light transmission from the outside. Now we need to calculate the amount of light inside our greenhouse.If we assume this, we can then calculate 50% from the total solar radiation data in order to get a close number for the light present outside the greenhouse. We learned light is about half solar radiation.We must then calculate a close number for the radiation environment inside the greenhouse. Data from the meteorological stations provide information about the radiation environment OUTSIDE the greenhouse.A conversion from energy units to PPFD will be required. Radiation sensors included in meteorological stations measure total global radiation in energy units.When getting data from a meteorological weather station outside a greenhouse we have the following problems to approach: How to calculate PAR inside my greenhouse with typical data from meteorological weather stations? Meteorological weather stations are located OUTSIDE the greenhouse. However PAR sensors are not as common as radiation sensors, which are usually already included in meteorological weather stations in greenhouses. This is why the best way to measure light will be with the help of a PAR sensor, also called Quantum Sensor. This specific unit will help us to really understand how plants are using light. When measuring PAR we use a specific unit called PPFD (Photosynthetic Photon Flux Density) measured in □mol/ m 2/s. PAR includes just a portion of solar radiation, from 400 nm to 700 nm. In order to understand how plants use light we use PAR (Photosynthetic Active Radiation). Light included in solar radiation includes all wavelengths visible to the human eye. Which is the best way to measure light in order to understand the impact of light in crops? To measure radiation we use energy units like Joules/m 2/s or W/m 2. Only 45% to 50% of solar radiation represents light, the rest of the wavelengths include UV radiation and heat. Solar radiation includes more than light. Solar radiation in Earth covers a range 300 to 1500 nm. To understand light, let’s first separate light from solar radiation definition. What is Solar Radiation or Global Radiation? This article has the purpose to guide you on the approach you can take when working inside of greenhouses to correctly calculate the amount of light your crop is receiving. When we understand light we can make smart decisions to promote the best environmental conditions to promote growth, development and yield in our crops. When working inside a growing system such as a greenhouse or a plant factory system we must have enough knowledge about light management.
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