Long vs Short light wavelength absorption

[jumphigh]

Hi all

I was reading through an astrophysics book{1} and there I came across this sentence:

" A dust cloud can either scatter or absorb light that passes through it. Since shorter wavelengths are affected more significantly than longer ones, a star lying behind the cloud appears reddened to an observer."

I do not understand why shorter wavelengths are affected more than longer wavelengths. I may be missing some basic relation but I can't figure it out right now.

Thanks

{1}: "An introduction to modern astrophysics", R. W. Carroll, D. A. Ostlie, page 439

 

[jumphigh]

hmm...I think it would be sth like this:

shorter wavelength -> higher energy particles -> more collision with dust cloud particles

is that correct?

 

[jumphigh]

well i found the answer before anybody answers me, i thought i should post it for future ref

same book, page 440 explains in detail about how shorter wavelength can be greater affected by the environment than long wavelengths.

As an example, the large ripples on a pond can travel along without being disturbed by the leafs and dust grains on the surface of the pond whereas small ripples get distorted.

I hope this post will be useful for someone in future.

 

[mfb]

To add a wikipedia link: Rayleigh scattering
The same mechanism is responsible for our blue sky.

 

[sardar]

Hello,

Thank you for bringing up this interesting topic. The phenomenon you are referring to is known as wavelength-dependent extinction, and it is a key concept in astrophysics. To understand why shorter wavelengths are affected more significantly than longer ones, we need to look at the properties of dust particles and the behavior of light.

Dust particles in space are typically small in size and have irregular shapes. When light passes through a dust cloud, it interacts with these particles in two ways: scattering and absorption. Scattering is when the light is redirected in different directions, while absorption is when the light is absorbed by the particles.

The amount of scattering and absorption depends on the size and composition of the dust particles, as well as the wavelength of the light. Shorter wavelengths, such as blue and ultraviolet light, have higher energies and are more easily absorbed by the dust particles. This is because the particles are small enough to interact with the shorter wavelengths, causing them to absorb and scatter the light more effectively.

On the other hand, longer wavelengths, such as red and infrared light, have lower energies and are less likely to interact with the particles. This means that they can pass through the dust cloud with less absorption or scattering, resulting in a reddening effect when observed from a distance.

In summary, the shorter wavelengths are affected more significantly because they are more easily absorbed and scattered by the dust particles in the cloud. This phenomenon is crucial to understanding the appearance of objects in space and is a key factor in determining the composition and properties of dust clouds.

I hope this explanation helps you understand the concept better. If you have any further questions, please don't hesitate to ask. Thank you for your interest in astrophysics.

Best regards,