SCATTERING OF LIGHT BY SMALL DROPS OF WATER

1943 ◽  
Vol 21a (12) ◽  
pp. 99-109 ◽  
Author(s):  
R. Ruedy
Keyword(s):  
Sharp Increase ◽  
Main Part ◽  
Scattered Light ◽  
Incident Light ◽  
Wave Length ◽  
Red Light ◽  
Great Strength ◽  
Scattering Of Light

When very small drops of water increase in size until their diameter is one-fourth of the wave-length of the incident light (2a/λ = 1/4), they scatter the light essentially according to Rayleigh's law for non-conducting particles. But when the diameter increases from λ/4 to λ/2, the intensity of light scattered along directions that point toward the source decreases almost to zero, the change being most marked between 2a/λ = 1/4 and 2a/λ = 3/8. The sharp increase in the proportion of scattered light with an increase in size, according to the sixth power of the radius, continues however in the directions along which the main part of the scattered light is radiated by the particle. As the scattering begins to deviate from that given by Rayleigh's law, colours other than blue appear with great strength; the dispersion of the colours increases with increasing size of the particles until mainly red light remains.

scholarly journals On the theory of scattering of light

1938 ◽  
Vol 166 (926) ◽  
pp. 425-449 ◽  
Keyword(s):  
Scattered Light ◽  
Incident Light ◽  
Incident Beam ◽  
The State ◽  
Reciprocity Relation ◽  
Scattering Of Light ◽  
Plane Parallel ◽  
Solid Media ◽  
State Of Polarization ◽  
Light Components

In a series of recent investigations R. S. Krishnan (1934-8) demonstrated the existence of a new effect which will be called the Krishnan effect. It relates to the state of polarization of the light scattered by certain liquid or solid media in directions normal to the incident beam. To describe the effect let us denote with π the plane parallel to the direction of observation and to that of the incident beam. Since in the experiment this plane is usually horizontal we denote by H the intensity of those scattered light components which vibrate parallel to this plane, and by V those vibrating normal to π. In a similar manner subscripts h or v indicate whether the incident light vibrates parallel or normal to the plane. We distinguish therefore (see fig. 1) the four light components H h , H v , V h and V v . Following Krishnan the depolarizations are defined by P h = V h / H h , p v = H v / V v , p u = ( H h + H v )/( V h / V v ). p u is the depolarization for natural incident light. For most liquids the observations give, in agreement with the theories of temperature scattering, H h = V h = H v , hence p h = 1, p u = 2 p v /(1+ p v ). The Krishnan effect is the observation that in a number of liquid and solid systems p h = V h / H h ≠ 1, and V h = H v . Krishnan has called (2) the reciprocity relation. All observations have given p h < 1, but none of the present theories exclude the possibility that p h may assume values larger than 1.

scholarly journals The scattering of light by turbid media.–Part I

1931 ◽  
Vol 131 (817) ◽  
pp. 451-464 ◽  
Keyword(s):  
Refractive Index ◽  
Incident Light ◽  
Wave Length ◽  
Turbid Media ◽  
Spherical Particles ◽  
Parallel Beam ◽  
Scattering Of Light ◽  
Total Transmission ◽  
Photometric Observations ◽  
Opal Glass

The investigation which follows was undertaken with the object of arriving at a theory of the scattering of light by dense turbid media, which would be applicable, in particular, to opal diffusing glasses. The theory is developed on fairly general lines and applies to a system composed of a large number of similar spherical particles of a dielectric suspended in a by medium, provided the relative refractive index is not far from unity. He expressions derived show how the total transmission and reduction of a sheet of a medium containing the particles depends on the following variables; the refractive index of the medium, the side and number of the particles and their refractive index, the wave-length of the incident light and its distribution, that is whether it is diffuse or in the form of a parallel beam, the absorption coefficient of the medium in which the particles are suspended, and the thickness of the sheet. In Part I the general theory is developed, and in Part II numerical values of the necessary coefficients are computed, As a check on the theory, the size and number of the particles in a certain opal glass are deduced from photometric observations of its transmission and rejection. These calculated values are shown to be in agreement with those obtained by direct observation.

scholarly journals The structure of molecules in relation to their optical anisotropy.—Part I

1925 ◽  
Vol 107 (744) ◽  
pp. 684-693 ◽  
Keyword(s):  
Optical Anisotropy ◽  
Scattered Light ◽  
Incident Light ◽  
Incident Beam ◽  
Electric Vector ◽  
Scattering Of Light ◽  
Structure Of Molecules ◽  
Weak Component ◽  
Principal Directions

One of the most significant facts relating to the scattering of light in gases is the imperfection of polarisation of the light scattered in a direction perpendicular to the incident beam. The late Lord Rayleigh and Born explained this phenomenon as being due to the optical anisotropy of the molecule, that is, to the fact that the polarisation induced in a molecule depends on its orientation with respect to the electric vector in the incident light. Lord Rayleigh’s theory does not go into the question as to how the anistropy arises, but merely assumes that there are in each molecule three principal directions of vibration, along which the induced polarisations are different. If A, B, C are the moments induced in a molecule when its three principal directions are respectively along the direction of the electric vector in the incident light, then the ratio of the weak component to the strong in the transversely scattered light is given by r = 2 (A 2 + B 2 + C 2 ) - 2 (AB + BC + CA) / 4 (A 2 + B 2 + C 2 ) + AB + BC + CA. We now possess reliable measurements of the imperfection of polarisation in many gases and vapours, from the work of Lord Rayleigh and of Raman and Rao. Recently there has been carried out at Calcutta further measurement of the same quantity, in a series of organic vapours, by Mr. A. S. Ganesan. Some of these results are collected together in Table I.

Photosynthetic light gradients and spectral régime within leaves of Medicago sativa

1989 ◽  
Vol 323 (1216) ◽  
pp. 411-421 ◽  
Keyword(s):  
Medicago Sativa ◽  
Scattered Light ◽  
Incident Light ◽  
Red Light ◽  
Probe Light ◽  
Spongy Mesophyll ◽  
Light Gradient ◽  
Fibre Optic Probe ◽  
Optic Probe ◽  
Sun Leaves

By using a fibre-optic probe, light gradients were measured at 450, 550 and 680 nm in sun leaves, 125 µm thick, of Medicago sativa L. cv. Armor. The space irradiances immediately beneath the leaf surface were 1.5-2.0 times greater than the incident light for these wavelengths, indicating that M. sativa leaves are efficient light traps. Although the palisade was only 60 µm thick, each light gradient declined steeply within this layer. More light appeared to be scattered in forward rather than backward directions and the spectral régime of the light fluxes depended upon their direction of travel within the leaf. Spectra for transmitted light were dependent upon depth within the leaf, whereas back-scattered light consisted of mostly green and far-red light at all depths, PAR (photosynthetically active radiation, 400-700 nm) within both the palisade and spongy mesophyll consisted mostly of green and far-red light, and the spongy mesophyll received only 0.11 of the PAR compared with the midregion of the palisade. Anomalous measurements within the palisade were traced to the epidermis, which was found to act as a mosaic of microlenses that focused light within the palisade layer. In M. sativa leaves, the light microenvironment, leaf anatomy and photosynthesis seem to be strongly interrelated.

scholarly journals Photomorphogenesis in the Picocyanobacterium Cyanobium gracile Includes Increased Phycobilisome Abundance Under Blue Light, Phycobilisome Decoupling Under Near Far-Red Light, and Wavelength-Specific Photoprotective Strategies

2021 ◽  
Vol 12 ◽  
Author(s):  
Gábor Bernát ◽  
Tomáš Zavřel ◽  
Eva Kotabová ◽  
László Kovács ◽  
Gábor Steinbach ◽  
...  
Keyword(s):  
Electron Transport ◽  
Growth Rates ◽  
Incident Light ◽  
Red Light ◽  
Photosynthetic Performance ◽  
State Transitions ◽  
Photochemical Quenching ◽  
Strong Light ◽  
Antenna Size ◽  
Moderate Growth

Photomorphogenesis is a process by which photosynthetic organisms perceive external light parameters, including light quality (color), and adjust cellular metabolism, growth rates and other parameters, in order to survive in a changing light environment. In this study we comprehensively explored the light color acclimation of Cyanobium gracile, a common cyanobacterium in turbid freshwater shallow lakes, using nine different monochromatic growth lights covering the whole visible spectrum from 435 to 687 nm. According to incident light wavelength, C. gracile cells performed great plasticity in terms of pigment composition, antenna size, and photosystem stoichiometry, to optimize their photosynthetic performance and to redox poise their intersystem electron transport chain. In spite of such compensatory strategies, C. gracile, like other cyanobacteria, uses blue and near far-red light less efficiently than orange or red light, which involves moderate growth rates, reduced cell volumes and lower electron transport rates. Unfavorable light conditions, where neither chlorophyll nor phycobilisomes absorb light sufficiently, are compensated by an enhanced antenna size. Increasing the wavelength of the growth light is accompanied by increasing photosystem II to photosystem I ratios, which involve better light utilization in the red spectral region. This is surprisingly accompanied by a partial excitonic antenna decoupling, which was the highest in the cells grown under 687 nm light. So far, a similar phenomenon is known to be induced only by strong light; here we demonstrate that under certain physiological conditions such decoupling is also possible to be induced by weak light. This suggests that suboptimal photosynthetic performance of the near far-red light grown C. gracile cells is due to a solid redox- and/or signal-imbalance, which leads to the activation of this short-term light acclimation process. Using a variety of photo-biophysical methods, we also demonstrate that under blue wavelengths, excessive light is quenched through orange carotenoid protein mediated non-photochemical quenching, whereas under orange/red wavelengths state transitions are involved in photoprotection.

Die Beeinflussung der Zellkerne in den Vorkeimen von Dryopteris filix-mas durch rote und blaue Strahlung

1963 ◽  
Vol 18 (7) ◽  
pp. 557-562 ◽  
Author(s):  
Rainer Bergfeld
Keyword(s):  
Protein Synthesis ◽  
Visible Light ◽  
Blue Light ◽  
External Factor ◽  
Wave Length ◽  
Red Light ◽  
Three Dimensional ◽  
Short Wave ◽  
Nuclear Volume ◽  
Short Wave Length

Morphogenesis and differentiation of fern gametophytes (Dryopteris filix-mas) are strongly controlled by light. “Normal” morphogenesis, i. e. formation of two- or three dimensional prothallia, can occur only under short wave length visible light (= blue light). In darkness and under long wave length visible light (= red light) the gametophytes will grow as filaments. The blue light dependent photoreactive system which controls morphogenesis seems to be located in the outer layers of the cytoplasm. The control of morphogenesis is causally connected with the increase of protein synthesis under the influence of blue light.In the present paper the influence of red and blue light on shape and volume of the nucleus in the fully grown basal cell of the young gametophyte of Dryopteris filix-mas has been investigated. In blue light the nuclei are more or less spherical, in red and in darkness they are spindle shaped. If the light quality is changed the shape of the nuclei is only slightly influenced; the nuclear volume, however, is drastically changed: increase of volume in the blue, decrease of nuclear volume in red and darkness. These reversible changes of nuclear volume under the influence of light, which are apparently correlated with changing rates of protein synthesis, are an impressive example for the control of nuclear properties by an external factor via the cytoplasm.

scholarly journals Photoselective Protective Netting Improves “Honeycrisp” Fruit Quality

Plants ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1708
Author(s):  
Sara Serra ◽  
Stefano Borghi ◽  
Giverson Mupambi ◽  
Hector Camargo-Alvarez ◽  
Desmond Layne ◽  
...  
Keyword(s):  
Fruit Quality ◽  
Scattered Light ◽  
Red Light ◽  
Light Transmittance ◽  
Light Spectrum ◽  
Growing Seasons ◽  
Color Development ◽  
Red Color ◽  
Bitter Pit ◽  
And Control

High temperatures, wind, and excessive sunlight can negatively impact yield and fruit quality in semi-arid apple production regions. Netting was originally designed for hail protection, but it can modify the light spectrum and affect fruit quality. Here, pearl, blue, and red photoselective netting (≈20% shading factor) was installed in 2015 over a commercial “Cameron Select® Honeycrisp” orchard. Our research objectives were to (1) describe the light quantity and quality under the colored nets compared to an uncovered control and (2) investigate the effect of Photoselective nets on “Honeycrisp” apple quality for two growing seasons. Light transmittance and scattering for each treatment were measured with a spectroradiometer, and samples for fruit quality analyses were collected at harvest. PAR (photosynthetic active radiation), UV, blue, red, and far-red light were lower underneath all netting treatments compared to an uncovered control. The scattered light was higher under the pearl net compared to other colors, while red and far-red light were lower under the blue net. For two consecutive years, trees grown under the photoselective nets intercepted more incoming light than the uncovered trees with no differences among the three colors. In both years, trees under red and blue nets had more sunburn-free (clean) apples than pearl and control. Red color development for fruit was lower when nets were used. Interestingly, bitter pit incidence was lower underneath red nets for both years. Other than red color development, “Honeycrisp” fruit quality was not appreciably affected by the use of netting. These results highlight the beneficial effect of nets in improving light quality in orchards and mitigating physiological disorders such as bitter pit in “Honeycrisp” apple.

scholarly journals Relation between Changes in Photosynthetic Rate and Changes in Canopy Level Chlorophyll Fluorescence Generated by Light Excitation of Different Led Colours in Various Background Light

2019 ◽  
Vol 11 (4) ◽  
pp. 434 ◽  
Author(s):  
Linnéa Ahlman ◽  
Daniel Bånkestad ◽  
Torsten Wik
Keyword(s):  
Steady State ◽  
Light Quality ◽  
Incident Light ◽  
Red Light ◽  
Intensity Level ◽  
Potential Candidate ◽  
Light Emitting ◽  
Background Light ◽  
Light Regimes ◽  
The Difference

Using light emitting diodes (LEDs) for greenhouse illumination enables the use of automatic control, since both light quality and quantity can be tuned. Potential candidate signals when using biological feedback for light optimisation are steady-state chlorophyll a fluorescence gains at 740 nm, defined as the difference in steady-state fluorescence at 740 nm divided by the difference in incident light quanta caused by (a small) excitation of different LED colours. In this study, experiments were conducted under various background light (quality and quantity) to evaluate if these fluorescence gains change relative to each other. The light regimes investigated were intensities in the range 160–1000 μ mol   m − 2   s − 1 , and a spectral distribution ranging from 50% to 100% red light. No significant changes in the mutual relation of the fluorescence gains for the investigated LED colours (400, 420, 450, 530, 630 and 660 nm), could be observed when the background light quality was changed. However, changes were noticed as function of light quantity. When passing the photosynthesis saturate intensity level, no further changes in the mutual fluorescence gains could be observed.

scholarly journals Stimulated Raman scattering in a non-eigenmode regime

2020 ◽  
Vol 8 ◽  
Author(s):  
Yao Zhao ◽  
Suming Weng ◽  
Zhengming Sheng ◽  
Jianqiang Zhu
Keyword(s):  
Raman Scattering ◽  
Stimulated Raman Scattering ◽  
Laser Energy ◽  
Scattered Light ◽  
Incident Light ◽  
Loss Mechanism ◽  
Constant Frequency ◽  
Electrostatic Wave ◽  
Particle In Cell ◽  
Stimulated Raman

Stimulated Raman scattering (SRS) in plasma in a non-eigenmode regime is studied theoretically and numerically. Different from normal SRS with the eigen electrostatic mode excited, the non-eigenmode SRS is developed at plasma density $n_{e}>0.25n_{c}$ when the laser amplitude is larger than a certain threshold. To satisfy the phase-matching conditions of frequency and wavenumber, the excited electrostatic mode has a constant frequency around half of the incident light frequency $\unicode[STIX]{x1D714}_{0}/2$ , which is no longer the eigenmode of electron plasma wave $\unicode[STIX]{x1D714}_{pe}$ . Both the scattered light and the electrostatic wave are trapped in plasma with their group velocities being zero. Super-hot electrons are produced by the non-eigen electrostatic wave. Our theoretical model is validated by particle-in-cell simulations. The SRS driven in this non-eigenmode regime is an important laser energy loss mechanism in the laser plasma interactions as long as the laser intensity is higher than $10^{15}~\text{W}/\text{cm}^{2}$ .

scholarly journals The molecular scattering of light in vapours and in liquids and its relation to the opalescence observed in the critical state

1922 ◽  
Vol 102 (715) ◽  
pp. 151-161 ◽  
Keyword(s):  
Critical Point ◽  
Critical State ◽  
Incident Light ◽  
Wave Length ◽  
Molecular Scattering ◽  
Avogadro’S Number ◽  
Quantitative Manner ◽  
The Mean ◽  
Good Agreement ◽  
Molecular Scattering Of Light

It has long been known that in the immediate vicinity of the critical state, many substances exhibit a strong and characteristic opalescence. In recent years, the phenomenon has been studied by Travers and Usher in the case of carefully purified CS 2 , SO 2 , and ether, by S. Young, by F. B. Young in the case of ether, and in a quantitative manner by Kammerlingh Onnes and Keesom in the case of ethylene. An explanation of the phenomenon on thermodynamic principles as due to the accidental deviations of density arising in the substance was put forward by Smoluchowski. He obtained an expression for the mean fluctuation of density in terms of the compressibility of the substance, and later, Einstein applied Maxwell’s equations of the electromagnetic field to obtain an expression for the intensity of the light scattered in consequence of such deviations of density. He showed that the fraction α of the incident energy scattered in the substance per unit volume is 8 π 3 /27 RT β ( μ 2 – 1) 2 ( μ 2 + 2) 2 /N λ 4 (1) In this, R and N are the gas constant and Avogadro’s number per grammolecule, β is the isothermal compressibility of the substance, μ is the refractive index and λ is the wave-length of the incident light. Keesom tested this formula over a range of 2·35° above the critical point of ethylene and found good agreement except very close to the critical point.

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