Radiometric Quantities: Physics of EM Wave Explained

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In summary, the relationship between radiometric quantities and the physics of EM waves involves the energy density of the wave, which is a time and position dependent value, and the Poynting vector, which is also time and position dependent. Within radiometry, there are other quantities such as radiant energy, radiant flux, and radiant energy density, which can be treated as functions of wavelength or integrated over a spectrum. These quantities are related through equations, such as the energy density being equal to half of the Poynting vector squared, and the radiant energy being equal to the radiant flux multiplied by area and time.
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Hello everyone,

I'm hoping someone can help me understand (in a most general fashion possible) a relations between radiometric quantities and physics of EM wave.

With EM wave quantities that are usually mentioned in books (at least the ones I've found) are:
- energy density of EM wave (this is a time dependent and position in space dependent value as far as I understand).
- Poynting vector (this is a time dependent and position in space dependent value as far as I understand).

Now within radiometry there are among others following quantities:
- Radiant energy
- Radian flux (also called radiant power)
- Radiant energy density

I understand that all of thos quantities can either be treated as a functions of wave length of "in total" - by integrating over a spectrum. So looking at them at a fixed wave length (so that each is a function of wave lenght) my question is - how those radiant quantities relate to physical quantities?

Thanks in advance

P.S. I'm not a physicist but a mathematician, so don't hesitate to put an equation or three in here :)
 
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The energy density of an EM wave is related to the Poynting vector by the following equation: Energy Density = (1/2)*(Poynting Vector)^2. Radiant energy, flux and energy density are all related by the following equation: Radiant Energy = Radiant Flux x Area x Time. Therefore, the radiant energy density is equal to the radiant flux divided by the area. Hope this helps!
 

1. What are radiometric quantities?

Radiometric quantities are physical quantities that are used to describe electromagnetic (EM) waves, such as energy, power, intensity, and flux. These quantities are measured in terms of units like joules, watts, and watts per square meter, and are important in understanding the behavior and properties of EM waves.

2. How are radiometric quantities related to EM waves?

Radiometric quantities are directly related to EM waves, as they describe the energy and power carried by these waves. For example, the energy of an EM wave is proportional to its intensity and the distance it travels, and can be calculated using the radiometric quantity of radiant flux. Thus, understanding radiometric quantities is crucial in understanding the physics of EM waves.

3. What is the difference between radiant energy and radiant flux?

Radiant energy refers to the total energy emitted by an EM wave, while radiant flux refers to the rate at which this energy is being emitted. In other words, radiant energy is a total quantity, while radiant flux is a quantity per unit time. Both of these quantities are important in understanding the behavior of EM waves.

4. How are radiometric quantities measured?

Radiometric quantities are typically measured using specialized instruments, such as radiometers and photometers. These instruments are designed to measure the energy and power of EM waves, and can provide accurate measurements for different types of EM waves, from radio waves to infrared and visible light.

5. What are some real-world applications of radiometric quantities?

Radiometric quantities have a wide range of applications in various fields, such as telecommunications, remote sensing, and medical imaging. For example, understanding the properties of EM waves through radiometric quantities is crucial in designing and optimizing wireless communication systems. In remote sensing, radiometric quantities are used to measure and analyze data from satellites and other sensors to study the Earth and its environment. In medical imaging, radiometric quantities are used to measure and analyze the radiation emitted by X-rays and other imaging techniques.

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