The following are explained : Radiation flux density, Photosynthesis photon flux density and Illuminance.
Fig. Relationship between wave length and color of light (spectrum) (Hoshi, original)
Fig. Relative value of the sensitivity per unit energy at each wavelength(Hayashi, 1996)
- (A)Radiation flux density(RFD)
It is the radiation flux density the result to of add the energy intensitity of the each every wavelength. Therefore, characteristics are flat even in which wavelength. However, it is greatly divided into 3000nm short wave radiation (6000K) and long wave radiation (300K) of 80um from 3000nm from 200nm by characteristics of the sensor. Then, the radiation flux density including the effective wavelength region for the photosynthesis calls it short wave radiation flux density, because it is measured by radiation sensor for the short wave radiation. In addition, the fact of radiation flux density measured using the filter which passed only 700nm effective wavelength range from 400nm for the photosynthesis is called the photosynthesis radiation flux density(PRFD). The unit uses Wm-2 and cal cm-2min-1, etc.. In this page, Wm-2 is used. By the way, The equation for converting is 1.0Wm-2~=0.0014cal cm-2min-1.
- (B)Photosynthesis photon flux density(PPF, PPFD)
Not energy but unit expressed at the number of the light quantum ( photon ) which is a particle of the light are photosynthesis light quantum flux density. The photosynthesis is influenced according to the number of the light quantum which is emitted to the chlorophyll. Generally, it the light quantum of the 8-10 piece in order to consume carbon dioxide ( carbon dioxide, CO2 ) of the monad of the photosynthesis. Then, it is photosynthesis light quantum flux density to show the number in which the light quantum at 700nm wavelength from 400nm which is the chlorophylloid absorption wave length area was emitted at unit time and per unit area. Energetic, the wavelength shortly and proportionally rise on the energy of ( the frequency is high ), because there is the relation of e=hn ( e : Energy h : Constant n : Frequency ). The unit is umol m-2s-1. 1 mol shows 6.02~1023.
- (C)Illuminance
The human eye the sensitivity which senses the light of the wavelength near 555nm green is the best, and then, it becomes dull, as the wavelength approaches red and purple. In short, the sensitivity color of orange, yellow, and green is good, and sensitivity such as red, blue, purple is low. Therefore, units of the brightness with the curve ( luminosity curve ) adjusted to the sensitivity of the human eye are necessary for the case in which the lighting of the intensity which is appropriate for homes and workshops, etc. is designed. This is the illuminance. The unit is lx ( lux ). The brightness of the plane which left 1m from the light source with 1cd ( candela ) luminous intensity becomes 1lx. Therefore, the illuminance must be called that it is the unit in which there is no relation at all on the photosynthesis of the plant, and that at the present, there is a problem on evaluating the light environment of the plant using this unit.
It puts the numerical value in one field by the appointment of the type of light source, and the calculation is possible, when "Calculate" button is pushed.
| Item | Light Source | PRFD | PPFD | Illuminance | |
|---|---|---|---|---|---|
| P | Wm-2 | umol m-2s-1 | lx |