Why do long wavelengths travel further than short wavelengths?

Click For Summary

Discussion Overview

The discussion centers around the reasons why longer wavelengths are perceived to travel further than shorter wavelengths, exploring various types of waves including sound waves and electromagnetic waves. Participants consider factors such as diffraction, absorption, and the characteristics of different wave types in different media.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that longer wavelengths, such as radio waves, are diffracted by the Earth's atmosphere, allowing them to "cling" to the surface, while shorter wavelengths tend to escape into space.
  • Others argue that low-frequency sound waves travel further than high-frequency sound waves due to greater absorption of the latter by air molecules.
  • There is a discussion about the need for precision in defining the type of waves being discussed, as sound waves require a medium while electromagnetic waves can travel through a vacuum.
  • Some participants propose that diffraction and absorption both play roles in determining how far waves travel, with a focus on the relative importance of each factor.
  • One participant raises questions about the characteristics necessary for diffraction to occur, particularly in relation to sound waves.
  • There is mention of "edge diffraction" and its potential effects on wave propagation, though clarity on this concept remains limited among participants.
  • Participants discuss the distinction between different types of water waves, including those governed by surface tension and capillary waves, and their implications for wave behavior.
  • One participant expresses uncertainty about the concept of absorption in the context of sound waves, questioning what it means for a molecule to absorb a sound wave.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the primary reasons for the differences in travel distance between long and short wavelengths. Multiple competing views remain regarding the roles of diffraction and absorption, as well as the types of waves being considered.

Contextual Notes

Limitations include varying definitions of wave types, the dependence on specific environmental conditions, and unresolved questions about the mechanisms of absorption and diffraction.

Firefox123
Messages
183
Reaction score
1
What is it that allows longer wavelengths to travel further than shorter wavelengths?

Is it because of diffraction properties or is it related to the energy of the wave?

Or perhaps a combination of several things...?

Thanks.


Russ
 
Science news on Phys.org
I think you're taking about radio waves aren't you? If I remember corrently, it's because longwave is diffracted by the Earth's atmosphere and so can 'cling' to the surface of the earth, whereas shortwave just goes out into space.
 
You are going to have to be a lot more precise! Sound waves?? or Electro-magnetic (light and radio) waves. In the atmosphere or open space (sound waves, of course, cannot exist without a medium- electromagnetic waves travel through open space any distance without regard to their frequency).

Low frequency (long wave length) sound waves in the atmosphere (or water- ask any whale!) travel farther than high frequency (short wave length) sound waves because the short wave lengths are more easily absorbed by the molecules in the air.
 
Hey |2eason...

Thanks for the reply...

|2eason said:
I think you're taking about radio waves aren't you? If I remember corrently, it's because longwave is diffracted by the Earth's atmosphere and so can 'cling' to the surface of the earth, whereas shortwave just goes out into space.

Radio waves would be one example...I was under the impression that this was also true for pressure/compression waves and for transverse waves such as water waves...

So is this true for waves in general...and if so, then why?



Russ
 
Hey there HallsofIvy...

HallsofIvy said:
You are going to have to be a lot more precise! Sound waves?? or Electro-magnetic (light and radio) waves. In the atmosphere or open space (sound waves, of course, cannot exist without a medium- electromagnetic waves travel through open space any distance without regard to their frequency).

Right...I wasnt trying to make a general connection between wavelength and distance...since, as you say, E-mag waves will travel through empty space independent of frequency...

I was looking more for general reasons a long wavelength would travel a longer distance than a short wavelength in some environment...I suspect it is related to the two things already mentioned in the responses thus far...diffraction and absorption...but I want to verify I am correct before I begin looking for specifics for various waves...

HallsofIvy said:
Low frequency (long wave length) sound waves in the atmosphere (or water- ask any whale!) travel farther than high frequency (short wave length) sound waves because the short wave lengths are more easily absorbed by the molecules in the air.

So for sound waves...is absorption the main difference? Does diffraction play an important role as well or is it secondary to absorption?

Thanks..


Russ
 
What's the main charateristics diffracted waves must have...?

Daniel.
 
Hey there dextercioby...

dextercioby said:
What's the main charateristics diffracted waves must have...?

Daniel.

Im not sure what you are asking by the question...are you asking me what I think the charateristics are that are necessary for diffraction to occur?

If that is the question then my answer would be the wavelength of the wave compared to the physical dimensions of the object that the wave is being diffracted around...

Am I understanding your question here or did you mean something else?



Russ
 
I meant exactly that.Now,if you know that,what can u say about diffracting sound waves...?

Daniel.
 
dextercioby said:
I meant exactly that.Now,if you know that,what can u say about diffracting sound waves...?

Daniel.

Well...I would say that it seems like the longer the wavelength of the wave...the less the wave will be distorted if it is diffracted around an object...



Russ
 
  • #10
Yes,it's all about the size of the objects encountered in the way.Water/air molecules are definitely not an issue for sound waves...And also big objects.Yet one may argue about "edge diffraction"...

Daniel.
 
  • #11
Short water waves governed by surface tension move swifter than longer capillary waves.
 
  • #12
dextercioby said:
Yes,it's all about the size of the objects encountered in the way.Water/air molecules are definitely not an issue for sound waves...And also big objects.Yet one may argue about "edge diffraction"...

Daniel.

So would you say that the main reason for the difference in distance is related to diffraction or would absorption be equally as important?

...I am not very familiar with "edge diffraction"...

Russ
 
  • #13
arildno said:
Short water waves governed by surface tension move swifter than longer capillary waves.

When you say a water wave governed by surface tension it sounds like you are implying that there are water waves governed by something other than surface tension...

Is this correct?

I really do not know what capillary waves are...I will have to look into that...

I don't know or understand a lot about physics, math, or engineering...so I am very much a beginner.





Russ
 
  • #14
steadele said:
So would you say that the main reason for the difference in distance is related to diffraction or would absorption be equally as important?

...I am not very familiar with "edge diffraction"...

Russ

The point i was trying to make was that in the case of the sound waves,it's more about "damping" via absorption as KE for the molecules,rather than diffraction and I've given you the reason;air molecules are much smaller than wavelengths of the sound waves... :wink:

Are u then familiar with the electromagnetic theory of light and especially scalar diffraction...?

Daniel.
 
  • #15
steadele said:
When you say a water wave governed by surface tension it sounds like you are implying that there are water waves governed by something other than surface tension...

Is this correct?

I really do not know what capillary waves are...I will have to look into that...

I don't know or understand a lot about physics, math, or engineering...so I am very much a beginner.
Russ
"Capillary waves" means the same as "water waves governed by surface tension".

And yes, for most water waves, gravity is the most important force governing wave propagation.
Capillary forces (i.e, the effects of surface tension) only become important (for water, that is) when the wavelengths are about 10-20 cm's or less.
 
  • #16
dextercioby said:
The point i was trying to make was that in the case of the sound waves,it's more about "damping" via absorption as KE for the molecules,rather than diffraction and I've given you the reason;air molecules are much smaller than wavelengths of the sound waves... :wink:

:smile: Ooops...I must have misread your reply...my mistake...

Since air molecules are so much smaller than the wavelengths of sound waves the effects due to diffraction are minimal...

To be honest I've never studied absorption of different wavelengths in any depth...

dextercioby said:
Are u then familiar with the electromagnetic theory of light and especially scalar diffraction...?

Emag theory...yes...I have a Bachelors in Electrical Engineering and have just started working towards my Masters with a focus in Electromagnetics (I work with antennas and radar in my civilian job)...but I am still very much a beginner at these topics...

As far as scalar diffraction...I do not remember ever studying that or even hearing that term before...so I am not sure what it is...



Russ
 
  • #17
The scalar theory of electromagnetic wave diffraction assumes the fields/potential to be scalar and from that builds the whole theory of Fresnel and Fraunhofer diffraction.About 350 pages in the book by Born & Wolf...

Daniel.
 
  • #18
What does it mean for a molecule to absorb a sound wave? I was under the impression that a sound wave existed by moving the molecules...does 'absorbing' mean the molecule just doesn't move?
 

Similar threads

Undergrad Why is Cherenkov radiation blue? And what about refractive index?
  • · Replies 3 ·
Replies
3
Views
3K
Graduate Light wavelength transmission through ice
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Why does wavelength affect diffraction?
  • · Replies 1 ·
Replies
1
Views
3K
High School Does Wavelength Affect Uncertainty in Macroscopic Objects?
  • · Replies 11 ·
Replies
11
Views
3K
Undergrad How can diffraction occur with gap smaller than the wavelength?
  • · Replies 1 ·
Replies
1
Views
10K
High School A silly question about why the sky is blue
  • · Replies 4 ·
Replies
4
Views
12K
Graduate How a very short λ enable light, not obliterate all shadow? (diffraction)
  • · Replies 14 ·
Replies
14
Views
2K
Undergrad Long vs Short light wavelength absorption
  • · Replies 3 ·
Replies
3
Views
9K
Graduate Diffraction pattern's dependency on wavelength
  • · Replies 2 ·
Replies
2
Views
3K
Undergrad Why Do Longer Wavelengths Go Slower in Glass?
  • · Replies 9 ·
Replies
9
Views
2K