bodhi said:please tell me if a photon of light is considered massless,then it should penetrate even walls,but that does not happen,then how can you consider light as massless??
According to what? Pokemon battle rules?bodhi said:thats because if you have no mass then nothing can block you.
bodhi said:thats bcoz if you have no mass then nothing can block you.
ZapperZ said:You appear to be making up your own rules and physical laws.
Zz.
DaleSpam said:bodhi and LostConjugate, I would recommend that you both read the following FAQ entries:
http://www.desy.de/user/projects/Physics/ParticleAndNuclear/photon_mass.html
https://www.physicsforums.com/showthread.php?t=511175
Passing through objects has nothing to do with mass. It has to do with interaction. Neutrinos have more mass than photons but penetrate much deeper through ordinary matter because they interact only very weakly.
LostConjugate said:If light had no mass (no energy) it would pass through objects sure. But it does have mass. You read that it can be treated as a particle with zero rest mass, this would mean that if it were at relative rest it would have no mass. As soon as it has any relative velocity it has energy and therefor is treated as a massive particle with momentum. Though most photons have such little mass (energy) that it does pass through walls.
Think of it this way, the more times it oscillates as it passes through the wall the less probability it has of making it to the other side. The energy (mass) is proportional to the rate of oscillation.
ZapperZ said:This is wrong.
Light has momentum, but no mass, as in invariant mass that we are familiar with. Do not make things up like this.
Passing through walls have nothing to do with having a mass or not. Neutrinos have mass, but they pass through the Earth with very little interaction!
Zz.
It certainly can depending on its speed, but regardless of the total energy it always has more mass.LostConjugate said:A neutrino has more total energy than a photon of say visible wavelength?
LostConjugate said:True, invariant mass doesn't have anything to do with passing through objects.
However even though bodhi may not be saying it the proper way. He is not wrong by thinking of mass as the limitation of passing through objects. The lower your energy the higher the probability of passing through an object without disturbing it.
He is wrong, and the statement that the lower the energy the higher the probability of passing through is not true in general. If it were true then absorption spectra would be monotonically decreasing with increasing wavelength instead of displaying peaks.LostConjugate said:He is not wrong by thinking of mass as the limitation of passing through objects. The lower your energy the higher the probability of passing through an object without disturbing it.
ZapperZ said:This is incorrect as well.
I can show you a band-pass filter in which a lower frequency of light will NOT pass through.
You are making things up.
Zz.
LostConjugate said:Ok ok, I stand corrected. I was thinking on a more fundamental level I suppose.
A simple potential barrier and a particle. The probability of passing through is proportional to a Gaussian of the energy.
Also was thinking of EM waves. A radio wave happily passes through the walls of your house while the EM wave coming from your lamp does not, and a X-ray tears it's way through. All of this of course the expectation value of a great number of photons meeting a great number of different potentials.
Edit: so maybe I don't stand corrected?? I don't know.
Again, what is important is the interaction. Suppose you have a thick block of scintillator crystal, then the x-ray will be strongly absorbed, the visible light somewhat absorbed, and the radio wave not absorbed very much, but instead suppose you have a large but very thin sheet of metal (or a wire mesh) then the radio wave will be completely absorbed, the visible light somewhat absorbed, and the x-ray will not be attenuated much at all. Completely opposite behavior because the interactions are different.LostConjugate said:Also was thinking of EM waves. A radio wave happily passes through the walls of your house while the EM wave coming from your lamp does not, and a X-ray tears it's way through. All of this of course the expectation value of a great number of photons meeting a great number of different potentials.
ZapperZ said:If you don't know, let me give you a strong advise: don't make things up and offer them as answers. Your original response was given with such certainty as if you know these things intimately. Instead, you're guessing!
People look up to this forum because it has a higher signal-to-noise ratio than other forums. Do NOT add to the noise.
Zz.
Light is a form of electromagnetic radiation that is visible to the human eye. It is made up of tiny particles called photons which travel in waves at the speed of light.
According to the current understanding of physics, yes, light is considered to be massless. This means that it does not have any physical mass or weight, unlike other particles such as electrons or protons.
Scientists have conducted numerous experiments and observations that have consistently shown that light behaves as a massless particle. Additionally, the theory of relativity, proposed by Albert Einstein, also supports the idea that light has no mass.
The famous equation E=mc², proposed by Einstein, states that mass and energy are equivalent and can be converted into each other. Photons, being massless particles, contribute to the energy side of this equation and are responsible for carrying energy in the form of light.
While light is considered to be massless in most situations, there are certain theories that propose the existence of a hypothetical particle called the "graviton" which would give light a very small amount of mass. However, this is still a topic of debate among scientists and has not been proven yet.