Is particle speed affected by source?

  • Context: Undergrad 
  • Thread starter Thread starter mananvpanchal
  • Start date Start date
  • Tags Tags
    Particle Source Speed
Click For Summary

Discussion Overview

The discussion revolves around the question of whether the speed of particles is affected by their source, comparing this to the behavior of sound and light. Participants explore concepts related to wave-particle duality, reference frames, and the implications of mass on speed.

Discussion Character

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

Main Points Raised

  • Some participants assert that sound speed is not affected by its source, while the speed of massive objects is influenced by their source.
  • One participant notes that light travels at speed c in all reference frames due to being massless, suggesting that this characteristic differentiates it from massive particles.
  • Another participant mentions that in quantum mechanics, if a particle has a well-defined mass and momentum distribution, its speed can be affected by its source.
  • A participant provides a relativistic velocity addition formula, indicating how the speed of a particle is calculated relative to different frames of reference.
  • There is a discussion about the wave-particle duality of heavy objects and electrons, with some participants confirming that heavy objects also exhibit this duality.
  • One participant summarizes the characteristics of sound, light, electrons, and heavy objects, noting their respective requirements for medium and how their speeds are affected by mass.

Areas of Agreement / Disagreement

Participants generally agree that light's speed is not affected by its source due to its massless nature. However, there are competing views regarding how the speed of particles, particularly massive ones, is influenced by their source, and the discussion remains unresolved on some aspects of wave-particle duality and the implications of mass.

Contextual Notes

Participants express uncertainty regarding the definitions and implications of wave-particle duality, the role of mass in speed, and the effects of reference frames on particle motion. Some mathematical steps and assumptions in the relativistic velocity addition are not fully resolved.

mananvpanchal
Messages
215
Reaction score
0
I have some basic understanding that:
Sound travels through air medium, and sound is in [pure wave form] (Please, correct [...] if wrong). Sound speed is not affected by its source.

Some heavy object fired by its source. The object doesn't need medium to travel. The object is in [pure particle form] (Please, correct [...] if wrong). The object's speed is affected by its source.

Light is in wave/particle form. Light doesn't need medium to travel. Light speed is not affected by its source.

But, I don't know this.
What about particles? Particles also are in wave/particle form. And they also don't need medium to travel. Is particle speed affected by its source?
 
Last edited:
Physics news on Phys.org
The reason light travels at c from all reference frames is because it's massless. (Well, technically, you can't have just one of these two criteria and not the other.) Massive particles' waves don't need a medium, but their speed is affected by their source. Think about all this in terms of time dilation and hopefully you'll understand me.
 
mananvpanchal said:
What about particles? Particles also are in wave/particle form. And they also don't need medium to travel. Is particle speed affected by its source?
When you are talking about QM these things are uncertain. If you have a particle with a well defined mass (eg an electron) and if the source produces those particles with a well defined momentum distribution, then yes, the particles speed is affected by it's source.
 
mananvpanchal said:
But, I don't know this.
What about particles? Particles also are in wave/particle form. And they also don't need medium to travel. Is particle speed affected by its source?

Yes, if a particle is ejected from e.g. a gun at velocity v relative to the gun at rest in frame S and the gun has a velocity of u relative to another frame S', then the particle velocity w in S' is given by:
[tex]w = \frac{u +v}{1+uv/c^2}[/tex]

For a photon where v=c the velocity w is always c for any value of u. For small u<<c and v<<c, the equations aproximates to the Newtonian w ≈ u + v.

Note that the relativistic velocity addition equation does not treat massive and massless particles differently. It is only concerned with their relative velocities.
 
Thanks guys.

Ok, so my main concern is I want to understand what is actually "motion".

Light's speed is not affected by source, as Whovian says and I also think that it is because photon doesn't have mass.
We have some examples like sound waves, light waves/matters, electron waves/matters, Heavy object matters. I had read somewhere that heavy object also have wave/particle duality, is this right? I am trying to connect all this thing by their characteristics.

Sound: waves - medium required - mass less - speed not affected.
Light: waves/matters - no medium - mass less - speed not affected.
Electron: waves/matters - no medium - with mass - speed affected.
Heavy Object: matters - no medium - with mass - speed affected.

I am actually trying to understand the relationship between above content. Is this good idea?
 
Light's speed is not affected by source, as Whovian says and I also think that it is because photon doesn't have mass.

yes

I had read somewhere that heavy object also have wave/particle duality, is this right?

yes...it's called DeBroglie wavelength:

http://en.wikipedia.org/wiki/Debroglie_Wavelength

Matter, mass, has an associated wavelength.
Sound: waves - medium required - mass less - speed not affected.
Light: waves/matters - no medium - mass less - speed not affected.
Electron: waves/matters - no medium - with mass - speed affected.
Heavy Object: matters - no medium - with mass - speed affected.

This summary of yours is ok. It's a 'good idea' if it helps you learn. I would mention that an electron IS a 'heavy object', so you can have just three categories.

You should probably remember that where a medium is required for transmission, the medium determines the speed of propagation. So with sound, for example, speed in water is different than speed in air.

Light [electromagnetic waves] is unique in that in a vacuum [no transmission medium]everyone measures its speed as 'c'. In other words, no matter how fast you are going, light always whizzes past you at 'c'. This takes some getting used to because it's not obvious from our everyday experience!
 
Thanks Naty1.
 

Similar threads

  • · Replies 22 ·
Replies
22
Views
2K
  • · Replies 19 ·
Replies
19
Views
2K
  • · Replies 59 ·
2
Replies
59
Views
6K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 17 ·
Replies
17
Views
2K
  • · Replies 36 ·
2
Replies
36
Views
3K
  • · Replies 22 ·
Replies
22
Views
2K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 51 ·
2
Replies
51
Views
5K