Questions tagged [radiometry]
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Demonstration of constant radiance for Lambertian Surfaces
I'm approaching to radiometry and I'm struggling with one of the properties of Lambertian surfaces.
We know that the radiance is the radiant flux emitted, reflected, transmitted or received by a ...
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Calculating radiance
I'm trying to understand how to calculate radiance ($L_{e,\nu}$), so I am using the sun/earth as a comparison as I have seen it stated that the radiance of sunlight is equal to:
$$
L_{e,\Omega} \...
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Formal mathematical definition of radiance and irradiance
Radiance is defined as
$$L = \frac{\partial^2 \Phi}{\cos{\theta} \partial A \partial\Omega}$$
and irradiance as
$$ E = \frac{\partial \Phi}{\partial A},$$
where $\Phi$ is the radiant flux, $\Omega$ is ...
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Lambertian surface and the luminous intensity
I am currently studying the basics of photometry to better understand the rendering equation of Kajiya. One thing I'm currently struggling with is Lambert's cosine law.
Let's go over the premises:
A ...
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Calculate Radiant Intensity from Radiant Power and estimated Radiant Distrubution of infrared LED [closed]
Consider the infrared led TSAL7600 which has the following properties:
$$ \Phi = 35 mW $$
$$ I_e = 25 mW/sr $$
The half angle is $30^\circ$ and:
$$ I_r(\theta) = cos^{4.818}(\theta) $$
is a good ...
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How to obtain mass attenuation coefficients of a compound given mass attenuation coefficients of separate elements?
Given a table of MACs for each element, like this one, is it possible to obtain a MAC for a chemical compound or solution? If so, how do I obtain one?
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Why does transversal magnetization decay and what is actually being measured in an MRI sequence? [closed]
This may be a few questions disguised as one however this may help uncover what's the missing piece in my understanding.
$T1$ characterizes the rate at which longitudinal $M_z$ recovers and $T2$ ...
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Spectral Irradiance of a Blackbody
This website states that the spectral irradiance of a Black Body is
$$F(\lambda) = \frac{2 \pi h c^2}{\lambda^5 (\exp (hc/k\lambda T)-1)}.$$
What does it mean to talk about "the" spectral ...
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Is this how to compute radiance for a point light source? How does this equation work?
I'm writing a ray tracer. Assumptions which led to this point:
Rays are in units of spectral radiance (watts per steradian per square metre) - this appears to be correct based on the subsequent maths ...
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What do the CIE Standard Illuminants SPDs represent?
The CIE publishes the relative SPD for standard illuminants. I was curious what photometric quantity it represents i.e. radiance or irradiance or something else.
I was reading the "Intro the ...
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Does radiant flux depend on solid angle?
I learned from various sources (e.g. Wikipedia) that the radiant flux $\Phi$ is the radiant energy emitted, reflected, transmitted, or received per unit time and is defined by:
$$\Phi(\mathbf{x},t) = {...
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Are radiance and luminance really independent of distance to observer?
Recently, I learned that apparently both radiance and luminance are independent of the distance between the light emitting object and the observer.
The reasoning was that although the radiant/...
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Relation between Radiance and Surface power density (i.e poynting vector intensity)
I am attending a microwave remote sensing course and I have same problem to understand the relation between the radiance and the intensity of poynting's vector.
The radiance is defined as:
$L(\theta,\...
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What is the irradiance of an extended source?
For example, what is the irradiance at a certain A = 2m^2 surface from a P = 10W tube lamp with significant radius and length - say, r = 15mm L = 100mm - measured at a small distance - say, d = 2m? ...
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The Event Horizon Telescope collaboration will announce groundbreaking observations of our galaxy at 12 May 2022, what this announcement could be? [closed]
"Live webcasting for the ESO-hosted EHT 2022 event
On 12 May 2022 at 15:00 CEST, the European Southern Observatory (ESO) will host a press conference on groundbreaking new Milky Way results from ...
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