# What is Radiative transfer: Definition and 18 Discussions

Radiative transfer is the physical phenomenon of energy transfer in the form of electromagnetic radiation. The propagation of radiation through a medium is affected by absorption, emission, and scattering processes. The equation of radiative transfer describes these interactions mathematically. Equations of radiative transfer have application in a wide variety of subjects including optics, astrophysics, atmospheric science, and remote sensing. Analytic solutions to the radiative transfer equation (RTE) exist for simple cases but for more realistic media, with complex multiple scattering effects, numerical methods are required.
The present article is largely focused on the condition of radiative equilibrium.

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1. ### What is the definition of Unit Optical Depth?

$$\chi = n \sigma$$ Where Chi is the Opacity, n is the number density of absorbers (constant), and $\sigma$ is the cross section(given). We define the optical depth is just the number of photon mean-free paths in a given physical step, i.e. if we consider a...

3. ### A Axisymmetric radiative transfer

Hi, I'm currently working on thermal radiation modelling in my PhD studies, and one thing that's under work is a cylindrical symmetric thermal radiation solver code. The idea is to solve the thermal radiation field in an absorbing medium between concentric cylinders as an essentially 1D problem...
4. ### Earth's Energy balance including a convective component

Hey guys, I'm really stuck right now 1. Homework Statement Habitable exoplanet: Now we will include a convective heat flux (H), with H being proportional to the difference between the atmospheric and ground surface temperature, $$H=c_p(T_a-T_p)$$ with c = 1.2 Wm−2K−1. Calculate the temperature...
5. ### Index of Refraction: Calculate ni for 10 cm Attenuation

Homework Statement Within a certain material, an EM wave with = 1 mm is attenuated to 10% of its original intensity after propagating 10 cm. Determine the imaginary part of the index of refraction ni Homework Equations 3. The Attempt at a Solution [/B] so...
6. ### Radiative Transfer Equation: Point Source and a Thin Lens

Homework Statement Write the Radiative Transfer Equation for an isotropic incoherent point source a distance p away from a thin lens. Assume that scattering in air can be ignored but absorption cannot be ignored. Homework Equations 1. Radiative Transfer Equation (RTE): \frac{dw}{dt} = \left[...
7. ### Radiative Transfer Parallel Plane Atmosphere Help

I've been working on this problem for about a week (mostly trying to understand it), I'm making little progress and it's due tomorrow. Any help or hints would be greatly appreciated. It's a long paragraph of a problem, so I'll try to summarize as best I can... Main Question: Derive an...
8. ### Reformulation of the Radiative Transfer Equations

for the following formulation of the RTE, Why do we reformulate in terms of μ = cosθ?
9. ### Radiative Transfer Semi-Infinite Series Alternating Slabs

Homework Statement Consider a semi-infinite, alternating series of thermally emitting planar slabs of two types. Type 1 slabs are at a temperature T_1 with optical depth \tau_1; Type 2 slabs are at a temperature T_2 with optical depth \tau_2. You observe the system at cm wavelengths where...
10. ### Radiative Transfer Homework: Slab of Stars & Dust | Get Help Now

Homework Statement A galaxy consist of a uniform slab of stars mixed with dust. The slab has thickness L, and optical depth \tau for a ray passing perpendicularly through the slab. assume the emmisivity of the stars \epsilon and the density of dust is constand throught the slab. Further assume...
11. ### Radiative Transfer + Emissivity

Homework Statement This isn't so much of a homework but rather I am trying to understand the physics. The solution to the radiative transfer for a isothermal homogeneous gas of layer consists of one part that describes the absorption and one part that describes the emission. My...
12. ### Radiative Transfer - Emitting Ring

Homework Statement Suppose there is an optically thin emitting ring with inner radius r_{in} and outer radius r_{out} seen edge on. Compute the relative surface brightness of the ring as a function of its projected position in the sky. Homework Equations Radiative transfer: dE = I_{\nu}...
13. ### Better explanation of Radiative Transfer in Atmosphere especially with Saturation

Re: the absorption & re-emission of long-wave radiation in the Earth's atmosphere. I thought it all made sense until I was trying to work out how to explain it better to others! So the Beer-Lambert equation describes the absorption at a given wavelength as exp(-k.z) where k is a constant...
14. ### Radiative transfer equation: Intensity from a disk.

Hello to everyone who reads, and thank you very much. 1. Problem: The actual problem is this: A thin disk with thickness 2H and radius R (H<<R), has an absorption co. "alpha" and emision co. j. Calculate the intensity I("miu", "tau"), where "miu" = cos("theta"), and "theta" is the angle...
15. ### Specific Intensity, Flux, Flux Density, Radiative Transfer

Hi, I'm new to the technical aspects of astronomy and I'm having trouble quantifying what the definitions of some of these terms are. I can find equations that relate most of them, but I'm not sure how to use any of them. The terms are specific intensity, flux, flux density, and monochromatic...
16. ### Radiative transfer to space affected by atmosphere?

I'm trying to model radiation losses from a flat surface facing the sky at night. If we ignore radiative absorption/emission in the atmosphere, the heat flux is the well-known Q=\epsilon\sigma(T_s^4-T_\infty^4) where we have the emissivity, the S-B constant, the temperature of the surface...
17. ### Radiative Transfer (Optically Thin Cloud)

Homework Statement An optically thin cloud at temperature T radiates power P_{\nu} per unit volume. Find an expression for the cloud's brightness I_{\nu} as a function of distance from the centre of the cloud in the case where: (a) the cloud is a cube of side d (b) the cloud is a sphere...