Absorption and Scattering of Light
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| License | CC Attribution - NonCommercial - NoDerivatives 3.0 Germany: You are free to use, copy, distribute and transmit the work or content in unchanged form for any legal and non-commercial purpose as long as the work is attributed to the author in the manner specified by the author or licensor. | |
| Identifiers | 10.3203/IWF/C-13094eng (DOI) | |
| IWF Signature | C 13094 | |
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| Production Year | 2004 |
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| IWF Technical Data | Video ; F, 6 min 6 sec |
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00:00
LightAbsorption (electromagnetic radiation)Particle physicsMeasurementGroup delay and phase delayAbsorption (electromagnetic radiation)LightScatteringIntensity (physics)
00:09
Refractive indexMaterialPhotometerReflexionskoeffizientExtinction (astronomy)Optical pathIntensity (physics)Absorption (electromagnetic radiation)Scattering
00:38
Intensity (physics)Absorption (electromagnetic radiation)ScatteringActive laser mediumFlightAbsorption (electromagnetic radiation)TypesettingHeatScatteringActive laser mediumIntensity (physics)LightArc lampCamera lens
00:59
GlassLightParticleContainment buildingArc lampPhotometerKosmischer StaubIntensity (physics)
02:05
LightPhotometerHull (watercraft)Intensity (physics)
03:12
Hull (watercraft)Intensity (physics)Opacity (optics)Absorption (electromagnetic radiation)
03:29
Absorption (electromagnetic radiation)Active laser mediumIntensity (physics)Absorption (electromagnetic radiation)Light
03:39
ScatteringActive laser mediumParticleDirect currentLightTypesetting
03:52
Light
04:09
GlassLightParticleWater vaporWavelength
04:33
ScatteringWavelengthWavelengthGruppensteuerung
04:38
LightSensorScatteringWavelengthGruppensteuerungIntensity (physics)
04:58
ScatteringWavelengthIntensity (physics)Power (physics)WavelengthScattering
05:16
Audio frequencyIntensity (physics)WavelengthPower (physics)ScatteringAudio frequencyWavelengthLightIntensity (physics)
05:28
Intensity (physics)Active laser mediumParticleScatteringDensityAbsorption (electromagnetic radiation)Extinction (astronomy)Absorption (electromagnetic radiation)LightParticleRemotely operated underwater vehicleWavelengthActive laser mediumExtinction (astronomy)Number densityNanotechnologyIntensity (physics)Cross section (physics)
06:06
Electric power distribution
Transcript: English(auto-generated)
00:03
Absorption and scattering of light. The intensity of a light source can be measured using a photometer. Bringing a transparent material into the optical path the intensity is only decreased by reflections in the surface. The
00:26
material can be described by its refraction index. If the intensity is decreased one needs another matter constant the extinction coefficient. This coefficient is composed of absorption and scattering and describes the
00:43
decrease of intensity inside a medium. At absorption the light entering the medium is converted into other types of energy mostly heat. To examine this phenomenon we use this setup. The light of a halogen lamp is bundled by a lens
01:09
and collimated by an iris. The bundled ray of light passes through a beaker glass and the intensity of the light is measured with a photometer. The
01:32
measuring device shows the intensity in lux. The potassium manganate solution in
01:41
this container goes through this tube which can be closed by a clip and into this beaker. Thus the light has to pass through a layer of increasing thickness. The particles in the solution are so small that practically no scattering occurs. During the experimental procedure one sees the
02:07
slowly filling beaker, the photometer and a diagram that shows the intensity of the light against the depth of the absorber. The exponential decrease is
03:15
clearly visible. A fitting graph gives the absorption coefficient of the
03:24
solution. This is described in general by Lambert's law of absorption. At
03:41
scattering the light is not converted to other types of energy but re-emitted in all directions. An analogous setup this time with the water-filled beaker is used to examine scattering. No light leaving the beaker can be seen because
04:12
the water as well as the glass are passed unhindered. But if milk is poured into the water a mixture with small particles is produced and the
04:24
light is scattered. Now the dependence of scattering from the wavelength is examined. One sees clearly that the red light with the longer wavelength is
04:43
scattered less than the blue light with a shorter wavelength. While only very little intensity from the red light is lost only 10% of the blue lights original intensity reaches the detector. Examining this with different wavelengths one sees that the scattering decreases with the increasing
05:05
wavelength. Plotting the wavelength in fourth power the correlation is obviously linear. Thus the scattering is inversely proportional to the fourth
05:21
power of the wavelength and proportional to the fourth power of the frequency. Using light of only one wavelength the decrease of intensity can be described as analogous to the absorption according to Lambert's law. The scattering coefficient is the product of the scattering cross-section that
05:43
describes the effective area of each particle in which the light is scattered completely and the number density of scattering particles per volume. In a medium where absorption and scattering occur the extinction coefficient is the sum of both constants.