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Light

J

JacobEvans

New Member
arg-fallbackName="JacobEvans"/>
Ok, I'm only in high school physics so bare with me....
We've been discussing light in class, and we've mentioned that light can be seen as both a wave and a particle. To my understanding it is a wave because it not only has things like a wavelength and amplitude, but also because it propagates and interacts with other waves by interference and what not.

But, why is it a particle? and please for the love of science use layman's terms as much as possible.
 
arg-fallbackName="Aught3"/>
No, I'm not going to do anything that involves getting 'bare' with you :lol:

My understanding

**Warning biologist talking about physics**

is that light is made up of photons which are particles, so light is actually a stream of particles. The reason people talk about wave/particle duality is that the stream of particles exhibits wave-like behaviour (e.g., double-slit experiment). The reason we notice the wave-like behaviour is that the particle (photon) is so small, and these effects occur in the micro or nano scale.
 
arg-fallbackName="JacobEvans"/>
I love you aught3! :lol: :lol:

and I think I understand, but is a photon really a particle or does it just have particle like characteristics?
 
arg-fallbackName="Aught3"/>
Ok, I had a quick read around the internet it is possible that my highschool physics is no longer current. Either that or I've come up with a totally new hypothesis, I vote we wait for a physicist.
 
arg-fallbackName="Ozymandyus"/>
Well, at least one of the clear particle properties of light is that it does not need a medium to propagate - any other sort of wave that is not consider a particle is described as waves In a Medium. Anything that can be transmitted across a vacuum is by definition a particle. Or a wave AND particle in this case =P.

Though I also am not a physicist, and it's been 9 years since I took college physics.
 
arg-fallbackName="JacobEvans"/>
I'm pretty sure it's not really a particle NOR a wave, it just has characteristics of both. I remember reading that though it's helpful to think of light as a wave or particle, it's only a model, in reality light is it's own 'thing'
 
arg-fallbackName="diagoras54"/>
It's not just light, it's all matter and energy. Light is made of photons, which, besides behaving like waves, have a wave function describing the probability of finding the particle at a certain location. When the precise location is measured, the wave function collapses and becomes a 100% probability of finding the photon there. This is why double-slit experiments have wave formations, which disappear when the locations of the particles are measured. Light is both a wave and a particle, and neither. This is not the realm of the easily understood.
 
arg-fallbackName="Aught3"/>
Is it the fact that photons have this wave function that makes them behave like waves?

Can you say something similar for of(other*) parts of the electromagnetic spectrum (e.g., radio waves)?

Edit: *what I meant to type
 
arg-fallbackName="Ozymandyus"/>
GoodKat said:
Light has mass, exerts force, and is affected by gravity.
Click to expand...
Light does not actually have mass (at least very probably does not), all waves are affected by gravity, and all waves can exert force.
JacobEvans said:
I'm pretty sure it's not really a particle NOR a wave, it just has characteristics of both. I remember reading that though it's helpful to think of light as a wave or particle, it's only a model, in reality light is it's own 'thing'
Click to expand...
Well, it depends on what you would mean by saying such a thing. A particle just has characteristics of a particle too, and it may have other characteristics we don't yet associate with particles. Does that mean it's not really a particle?

But if it helps you clarify things in your mind, no, the elementary particles that exhibit characteristics of waves should not be called waves or particles. Instead of saying wave particle duality you can say whatever you want to get everyone to agree to, but those are the terms physicists use at the moment to my knowledge. I believe wavicle has been tossed around before, though not sure if that was referring to something else.

In any case, photons are not the only things that exhibit this duality. Electrons,and other elementary particles etc behave in this same manner. Photons are a little special in that they have no discernable mass, but I believe there are some other elementary particles that also behave as waves and particles and have no discernable mass.
 
arg-fallbackName="JBeukema"/>
Aught3 said:
Can you say something similar for of parts of the electromagnetic spectrum (e.g., radio waves)?
Click to expand...
visible light is a part of the EM spectrum.

diagoras54 said:
This is not the realm of the easily understood.
Click to expand...
I wonder if anyone really understands it...
 
arg-fallbackName="diagoras54"/>
The wave function is likely the cause of the wave behaviour; it's most prevalent on large scales, and the uncertainty principle says that the more precisely we know the position of a particle, the less we know about its velocity, and vice versa. The same applies to the wave function: the more precisely we measure the position the more it behaves like a particle, until, when the location is measured exactly, it behaves solely like a particle. The double-slit experiments show that until we precisely know where the particle is, it behaves like a wave.
All electromagnetic radiation is photons, i.e. light, and the only difference is wavelength.
 
arg-fallbackName="GoodKat"/>
Ozymandyus said:
Light does not actually have mass (at least very probably does not), all waves are affected by gravity, and all waves can exert force.
Click to expand...
You sure? Waves aren't actually sucked in my gravity are they?
 
arg-fallbackName="diagoras54"/>
GoodKat said:
Light has mass, exerts force, and is affected by gravity.
Click to expand...
If photons had mass, they would be unable to travel at the speed of light; otherwise they would require infinite energy to accelerate them to that speed.
Ozymandyus said:
In any case, photons are not the only things that exhibit this duality. Electrons,and other elementary particles etc behave in this same manner. Photons are a little special in that they have no discernable mass, but I believe there are some other elementary particles that also behave as waves and particles and have no discernable mass.
Click to expand...
Everything behaves in this manner, both matter and energy, but on the large scales the probabilities cancel each other out. The wave functions neutralize, and the probability of finding that object in a particular location becomes something along the lines of 99.999999999999999999999999999999999999%, or essentially 100%.
 
arg-fallbackName="diagoras54"/>
GoodKat said:
You sure? Waves aren't actually sucked in my gravity are they?
Click to expand...
It's not that they're sucked in, it's that they follow the curvature of space, which is a result of gravity warping spacetime.
 
arg-fallbackName="Ozymandyus"/>
r00tcause said:
Is space not a vacuum? Can radio waves not be transmitted through space? Are radio waves therefore particles?
Click to expand...
Yes, space is a vacuum and yes radio waves are particles(photons).. as diagoras mentioned they are part of the electromagnetic spectrum.
 
arg-fallbackName="GoodKat"/>
diagoras54 said:
It's not that they're sucked in, it's that they follow the curvature of space, which is a result of gravity warping spacetime.
Click to expand...
I guess you learn something every day.
 
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