PAM (pulse amplitude modulation) fluorometers can be used to estimate the electron transport rate (ETR) [μmol(e-) m-2 s-1] from photosynthetic yield determinations, provided the absorptance (Abtλ) of the photoorganism is known. The standard assumed value used for absorptance is 0.84 (leaf absorptance factor, AbtF). We described a reflectance-absorptancetransmittance (RAT) meter for routine experimental measurements of the actual absorptance of leaves. The RAT uses a red-green-blue (RGB) LED diode light source to measure absorptances at wavelengths suitable for use with PAM fluorometers and infrared gas analysers. Results using the RAT were compared to Abtλ spectra using a Taylor integrating sphere on bird’s nest fern (Asplenium nidus), banana, Doryanthes excelsa, Kalanchoe daigremontiana, and sugarcane. Parallel venation had no significant effect upon Abt465 in banana, Doryanthes, a Dendrobium orchid, pineapple, and sugarcane, but there was a slight difference in the case of the fern A. nidus. The average Abt465 (approximately 0.96) and Abt625 (approximately 0.89) were approximately 14% and 6% higher than the standard value (AbtF = 0.84). The PAR-range Abt400-700 was only approximately 5% higher than the standard value (approximately 0.88) based on averaged absorptance from the blue, green, and red light data and from where the RGB-diode was used as a ‘white’ light source. In some species, absorptances at blue and red wavelengths are quite different (e.g. water lily). Reflectance measurements of leaves using the RAT would also be useful for remote sensing studies., R. J. Ritchie, J. W. Runcie., and Obsahuje bibliografii
In radiometric measurement of the object temperature, in measurement and evaluation of heat escape from buildings we meet with materials, which can be characterised as transparent or semitransparent. One of them is glass. The objective of the present article is to analyse glass features, including emissivity in dependence to wavelength and temperature and also the thermal transmissivity of glass. and Pri bezkontaktných meraniach teploty objektov, pri meraní a vyhodnotení úniku tepla z budov sa stretávame s materiálmi, ktoré možno označiť ako priezračné alebo polopriepustné. Jedným z bežne používaných materiálov je sklo. V príspevku sa pokúšame analyzovať vlastnosti skla, jeho emisivitu v závislosti na vlnovej dĺžke a teplote.