Relationship between wavelength and concentration of particles

[angela6884]

What is the relationship between the wavelength produced by a laser and the concentration of particles in the air? Does the wavelength get larger if the concentration of particles the beam hits increase?

 

[hutchphd]

There is no relationship that I know of nor any way to cause one.
Please you should tell us what prompts the question.

 

[etotheipi]

You can look at phenomena like Rayleigh scattering; i.e. the rate of attenuation of a laser beam can be related to quantities like the number density of particles in the air and the scattering cross-section (inversely proportional to the fourth power of wavelength I think?). I can't remember what the exact relations are off the top of my head.

It might not be what you're after, though.

 

[angela6884]

There is no relationship that I know of nor any way to cause one.
Please you should tell us what prompts the question.

Oh, I was just curious because I know that reflection nebulae, when there is more interstellar dust around, the nebula reflects more of the light from nearby stars.

 

[angela6884]

You can look at phenomena like Rayleigh scattering; i.e. the rate of attenuation of a laser beam can be related to quantities like the number density of particles in the air and the scattering cross-section (inversely proportional to the fourth power of wavelength I think?). I can't remember what the exact relations are off the top of my head.

It might not be what you're after, though.

Thanks! I'll look into it!

 

[hutchphd]

What does this have to do with the wavelength produced by a laser?

 

[etotheipi]

What does this have to do with the wavelength produced by a laser?

Yeah, I'd say the best bet is to read the label

Oh, I was just curious because I know that reflection nebulae, when there is more interstellar dust around, the nebula reflects more of the light from nearby stars.

It's going to be scattering of some variety of light from a star. The amount of scattering will naturally be proportional to the number of particles there to scatter it. Perhaps try googling some of these scattering mechanisms!

 

[angela6884]

What does this have to do with the wavelength produced by a laser?

Like if I took a spectrometer and looked at the beam of the laser, would the wavelength increase of decrease depending on the amount of particles in the air?

 

[etotheipi]

Like if I took a spectrometer and looked at the beam of the laser, would the wavelength increase of decrease depending on the amount of particles in the air?

For the wavelength of any individual photon to change you need it to undergo an interaction of some sort; this interaction must be specified.

Rayleigh scattering is essentially elastic scattering and the wavelength of the emitted light is the same. It's scattered in different directions, however, so all you'll notice is a drop in intensity. Other scattering processes can be inelastic.

To really answer the question more detail about the experimental setup is required.

 

[angela6884]

For the wavelength of any individual photon to change you need it to undergo an interaction of some sort; this interaction must be specified.

Rayleigh scattering is essentially elastic scattering and the wavelength of the emitted light is the same. It's scattered in different directions, however, so all you'll notice is a drop in intensity. Other scattering processes can be inelastic.

To really answer the question more detail about the experimental setup is required.

Oh ok, so is it the intensity being affected? Not the wavelength?

 

[etotheipi]

Oh ok, so is it the intensity being affected? Not the wavelength?

Depends on the scattering process. For a laser beam through a system of particles, where the only interaction is Rayleigh scattering, and there is a detector in the path of the beam on the other end. I believe that's a reasonable evaluation. You'll need to look into the details for reflection nebulae, however!

 

[angela6884]

Depends on the scattering process. For a laser beam through a system of particles, where the only interaction is Rayleigh scattering, and there is a detector in the path of the beam on the other end. I believe that's a reasonable evaluation. You'll need to look into the details for reflection nebulae, however!

Ok thank you so much!

 

[hutchphd]

Like if I took a spectrometer and looked at the beam of the laser, would the wavelength increase of decrease depending on the amount of particles in the air?

In general no. If the particles are moving at very high speeds there can be some relativistic effects that would cause shifts.

 

[angela6884]

In general no. If the particles are moving at very high speeds there can be some relativistic effects that would cause shifts.

Interesting!

 

[angela6884]

What does this have to do with the wavelength produced by a laser?

Hmm, what about is there a relationship between the concentration of particles in the air and the wavelength reflected off (not scattered) the particles?

 

[jtbell]

What is the relationship between the wavelength produced by a laser and the concentration of particles in the air? Does the wavelength get larger if the concentration of particles the beam hits increase?

By "particles", do you mean dust particles etc. floating in the air, or do you mean air molecules (O₂, N₂, etc.)?

 

[angela6884]

By "particles", do you mean dust particles etc. floating in the air, or do you mean air molecules (O₂, N₂, etc.)?

I'm thinking interstellar medium which are incredibly small and composed of iron, silicates, etc.