In physics, optical depth or optical thickness is the natural logarithm of the ratio of incident to transmitted radiant power through a material.
Thus, the larger the optical depth, the smaller the amount of transmitted radiant power through the material.
Spectral optical depth or spectral optical thickness is the natural logarithm of the ratio of incident to transmitted spectral radiant power through a material. Optical depth is dimensionless, and in particular is not a length, though it is a monotonically increasing function of optical path length, and approaches zero as the path length approaches zero. The use of the term "optical density" for optical depth is discouraged.
In chemistry, a closely related quantity called "absorbance" or "decadic absorbance" is used instead of optical depth: the common logarithm of the ratio of incident to transmitted radiant power through a material, that is the optical depth divided by ln 10.
Optical depth of a material, denoted , is given by:where
is the radiant flux received by that material;
is the radiant flux transmitted by that material;
is the transmittance of that material.
The absorbance is related to optical depth by:
Spectral optical depth in frequency and spectral optical depth in wavelength of a material, denoted and respectively, are given by:
where
is the spectral radiant flux in frequency transmitted by that material;
is the spectral radiant flux in frequency received by that material;
is the spectral transmittance in frequency of that material;
is the spectral radiant flux in wavelength transmitted by that material;
is the spectral radiant flux in wavelength received by that material;
is the spectral transmittance in wavelength of that material.
Spectral absorbance is related to spectral optical depth by:
where
is the spectral absorbance in frequency;
is the spectral absorbance in wavelength.
Attenuation
Optical depth measures the attenuation of the transmitted radiant power in a material. Attenuation can be caused by absorption, but also reflection, scattering, and other physical processes.
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.
In physics, optical depth or optical thickness is the natural logarithm of the ratio of incident to transmitted radiant power through a material. Thus, the larger the optical depth, the smaller the amount of transmitted radiant power through the material. Spectral optical depth or spectral optical thickness is the natural logarithm of the ratio of incident to transmitted spectral radiant power through a material.
Astronomy is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, meteoroid, asteroid, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates beyond Earth's atmosphere.
Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre (W/m2) in SI units. Solar irradiance is often integrated over a given time period in order to report the radiant energy emitted into the surrounding environment (joule per square metre, J/m2) during that time period. This integrated solar irradiance is called solar irradiation, solar exposure, solar insolation, or insolation.
Theoretical and practical course on experimental techniques for observation and measurement of physical variables such as force, strain, temperature, flow velocity, structural deformation and vibratio
Cosmology is the study of the structure and evolution of the universe as a whole. This course describes the principal themes of cosmology, as seen
from the point of view of observations.
We present constraints on neutrino masses, the primordial fluctuation spectrum from inflation, and other parameters of the ACDM model, using the one-dimensional Ly alpha-forest power spectrum measured
Ozone (O3) and aerosols are harmful to human health. Long-range transport sources contribute to the background levels upon which local pollution builds. The goal of this thesis is to describe and quan
Atmospheric trace gases and aerosols and climate interact in many ways. A quantitative assessment of the influence of trace gases and aerosols on climate can only be achieved if the interactions and f