# How Does Kirchoff's Law Relate to Spectrum Intensity and Wavelength?

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• SebastianRM
In summary: If the gas is not moving at the same speed as the observer, the wavelength of the light can be altered due to the Doppler effect. So, the color may appear to change, but it is actually just the wavelength shifting due to the motion of the gas. In summary, The author is discussing how the energy loss of electrons in a substance leads to the emission of photons, and how this can be used to identify the elements present in a spectrum. They also mention how amateur astronomers can contribute to scientific studies through spectroscopy. In addition, they explain how scattering can impact the appearance of a spectrum and how the Doppler effect can cause a shift in the wavelength of light.
SebastianRM
TL;DR Summary
In the book Foundations of Astrophysics (R&P) chapter 5, section 5.2.
It states: "A solid, liquid or dense gas produces a continuous spectrum".
What is the author meaning by that, I literally just read in section 5.1, that the depending on the energy loss of the electrons that make up the substance, this energy will be released as photons. Since this is particular for each atom, it explained how we can tell which element is wich.
So if the spectrum is Intensity vs Wavelength, how is it that the first statement is true.

In those media the photons undergo lots of scattering which reduces their energy and as a result, tends to smooth out the spectrum.

A spectrum looks like a hump with a long tail. There will usually be little spikes. If the spikes are pointing up (more intense) they are emission. If the spikes are pointing down they are absorption. The hump itself is a continuous spectrum. The spikes tell you what elements or compounds are involved. Sometimes a computer will delete the background so it looks like a graph of just spikes.
Sometimes the signal from the spike is large enough that you cannot see any background or black body emission on the graph. It is still there if you zoom in.

anorlunda
Thank you

SebastianRM said:
Summary: In the book Foundations of Astrophysics (R&P) chapter 5, section 5.2.
It states: "A solid, liquid or dense gas produces a continuous spectrum".

So if the spectrum is Intensity vs Wavelength, how is it that the first statement is true.
That statement is oversimplified. Any source hot enough to be seen by virtue of its internally generated energy will be mostly black body but additional absorption and emission spectra from the outer parts will always be detectable.
I have a friend who does astrophotography and he has taken up spectroscopy. It's really not to hard for an amateur; you use a slit over the star of interest, followed by a diffraction grating. You get a pretty looking spectrum and the image data shows absorption lines and bands. All that's in his back garden.

sophiecentaur said:
That statement is oversimplified. Any source hot enough to be seen by virtue of its internally generated energy will be mostly black body but additional absorption and emission spectra from the outer parts will always be detectable.
I have a friend who does astrophotography and he has taken up spectroscopy. It's really not to hard for an amateur; you use a slit over the star of interest, followed by a diffraction grating. You get a pretty looking spectrum and the image data shows absorption lines and bands. All that's in his back garden.
They can do more than pretty spectra with amateur spectrocopists contributing to real science include studies of Be stars, classification of supernova, monitoring of symbiotic stars and much more all with back garden observatories .
Regards Andrew

sophiecentaur
andrew s 1905 said:
They can do more than pretty spectra with amateur spectrocopists contributing to real science include studies of Be stars, classification of supernova, monitoring of symbiotic stars and much more all with back garden observatories .
Regards Andrew
Amateur astronomers have a vast potential for contributing to Space Science because there are so many different targets available, most of which cannot be observed by the expensive professional experiments.
Amateur naturalists have a similar potential for ground breaking observations.

andrew s 1905
mathman said:
In those media the photons undergo lots of scattering which reduces their energy and as a result, tends to smooth out the spectrum.
I cannot understand how the wavelength of an emission could alter as it is weakened. We do not see colour change with distance.

tech99 said:
I cannot understand how the wavelength of an emission could alter as it is weakened. We do not see colour change with distance.
Inelastic scattering would take energy from or add it to photons (hot gas).

tech99

## 1. What are Kirchoff's Laws for spectrum?

Kirchoff's Laws for spectrum are two fundamental principles that govern the behavior of electromagnetic radiation. They are the Law of Conservation of Energy, which states that the total energy of a closed system remains constant, and the Law of Conservation of Flux, which states that the total amount of energy passing through a surface remains constant.

## 2. How do Kirchoff's Laws apply to the study of light and other electromagnetic radiation?

Kirchoff's Laws are essential in understanding the behavior of light and other forms of electromagnetic radiation. They help us understand how energy is transferred and conserved in different materials and how light interacts with matter.

## 3. Can you explain Kirchoff's First Law for spectrum?

Kirchoff's First Law, also known as the Law of Conservation of Energy, states that the total energy of a closed system remains constant. In terms of light and other electromagnetic radiation, this means that the total amount of energy emitted by a source is equal to the total amount of energy absorbed by the surrounding environment.

## 4. How does Kirchoff's Second Law for spectrum relate to Kirchoff's First Law?

Kirchoff's Second Law, also known as the Law of Conservation of Flux, states that the total amount of energy passing through a surface remains constant. This law is closely related to Kirchoff's First Law, as it explains how the energy from a source is distributed and conserved as it travels through different materials.

## 5. How are Kirchoff's Laws for spectrum used in practical applications?

Kirchoff's Laws are used in a variety of practical applications, including the design of optical systems, the study of atmospheric and astronomical phenomena, and the development of technologies such as solar panels and optical fibers. They also play a crucial role in the analysis of spectroscopy data, which is used in fields such as chemistry, physics, and astronomy.

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