Note that the most efficient scattering of radiation occurs when the particle radius is about equal to the radiation wavelength, and that for radiation with much shorter wavelengths, scattering is inefficient, while the scattering for radiation with longer wavelengths is almost as small. For small size parameters, the scattering cross section, which is just a scattering strength, is proportional to the particle radius to the sixth power and the inverse of the radiation wavelength to the fourth power.
Equation tells us that blue radiation is scattered much better than red radiation. And quite a bit of the radiation is scattered to the side. In fact, this more efficient scattering of blue is part of the reason that the sky is blue, but that the sun appears to be yellow when high in the sky, and even red when setting.
When you feel you are ready, take Quiz You will be allowed to take this quiz only once. Good luck! Skip to main content. Print 6. Graph of size parameter x and type of scattering as a function of radiation wavelength and particle radius.
Radiation and particle types are shown at the right and top, respectively. Scattering patterns by spheres for different values of the size parameter x. The source is on the left so that radiation is traveling from left to right. Sunscreens used for the protection of human skin against the harmful effects of solar radiation contain UV absorbers as key ingredients, which are either dissolved in one of the phases of the preparation or, when insoluble, suspended as particles.
Although the UV protective effect of particulate UV filters, inorganic and organic, is mainly due to absorption, they scatter UV and visible light. The scattering can have an additional attenuating effect on the incoming radiation by increasing the pathlength of the photons, especially when soluble filters are also present.
This interval should not overlap with any absorption bands in the spectrum but merely define the red part of the spectrum where the absorption is known to be 0 in absence of scatter. Any additionally selected points '3' below define single data points that are added to the data range. These additional points are positioned at higher-energy wavelengths i.
Press the 'Fit' button located below the 'Absorption baselines' data listbox. The fitted scatter-function is now added to the Absorption baselines listbox and, if selected, plotted in the absorption window in black. Since only a small spectral region can usually be used in the fitting, and the scatter function increases dramatically at lower wavelength as shown in the first figure above, this fitting procedure could well result in a fit that does not at all represent scatter.
It is thus important that the fitted scatter baseline is below the absorption spectrum throughout the entire spectrum which must be checked manually. If the fit is bad at higher energies, you can try to use a fit function with a less steep wavelength dependency. Scroll to the "Alternate" or "Linear" fit functions do this next to the Fit button below the listbox and use one of these scatter functions instead. The three possible scatter fit functions are:.
While the latter two functions are not physically meaningful they do not depend just as dramatically on the wavelength. This is an advantage when a narrow data range is available for fitting i. Below is shown each of the fits obtained using the three different scatter functions:. In order to subtract the newly produced scatter baseline press the subtract button located below the 'Absorption spectra' data listbox. This will open a dialog box. In the right listbox you select the baseline to subtract from all absorption spectra selected in the left listbox.
Press OK. More Information. Calculate spectral overlap integral in FRET. Decompose spectra with multiple components. Fit Gaussian to spectral band. Integrate absorption and emission spectra. Quantum yields. Raman peaks in emission spectra. Scatter in UV-Vis absorption spectra.
Singular value decomposition SVD. Calculate fluorescence quantum yield. Create Gaussian spectrum. UV-Vis absorption reaction curves.
Custom operations: Navigating the command board of a e. Download absorption and emission spectra from online database. Export figures. Format input data. Import data from Origin project.
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