Pedantic - not soWhat colour is an Orange in the dark?
While this is fun, it's all pedantry.
Actually an Orange in the dark has no colour.Pedantic - not so
Colour of orange in the dark or under a blazing sun - it is the colour it is
What colour is it PERCEIVED to be - depends on how it is lit up
Is, the above, not what I expressed in far fewer words?What Color Is An Orange In The Dark?
If you keep a ripe orange in one corner of your room that gets variable amounts of light as the day passes, you will see different intensities of the color orange on the piece of fruit. Perhaps the difference isn’t too evident for you, since you won’t be staring at the orange all day, but another exercise you can try is holding an orange in front of a bright torch. Believe it or not, but it will turn a bright flaming red!
Put that same orange under a purple light and it will appear scarlet, but under blue light, it will appear brown. Has your orange turned into a chameleon? No, of course not, but why is it changing color? The orange will change color in all these situations because, as vision scientists put it, color is not a property of an object. Color exists in our head!
more at link....
Colour of orange in the dark or under a blazing sun - it is the colour it is
What colour is it PERCEIVED to be - depends on how it is lit up
Would it be more correct to say "it depends on how the brain translates the perceived wavelengths into colors"?What colour is it PERCEIVED to be - depends on how it is lit up
The above says that in the first instant, the "perceived" colour of anything depends on the EMS falling on it.Is, the above, not what I expressed in far fewer words?
Seriously?Would it be more correct to say "it depends on how the brain translates the perceived wavelengths into colors"?
The above says that in the first instant, the "perceived" colour of anything depends on the EMS falling on it.
Colour of orange in the dark or under a blazing sun - it is the colour it is
What colour is it PERCEIVED to be - depends on how it is lit up
Actually an Orange in the dark has no colour.
Colour in the first instant is determined by what part of the EMS is falling on that object, and what part of the EMS it actually reflects.
I don't believe we perceive colors at all. We perceive wavelengths which are translated into electro-chemical signals and when processing the information, the brain makes a best guess of what color these wavelengths represent.Seriously?
Please explain the difference in concept behind the words expression (apart from spelling)
I don't believe we perceive colors at all. We perceive wavelengths which are translated into electro-chemical signals and when processing the information, the brain makes a best guess of what color these wavelengths represent.
It's not always right .
Remember the chess board with the two squares which are identical in color, but the brain is unable to see them as the same color.
A and B are identical in color!
It is impossible for the brain to see these two squares as being the same color. The brain always tries to correct for shadow and cannot override this internal adjustment process.
(Its a survival tool)
The board is designed to demonstrate the effect of shadow in our perception. It's our brain that tricks us.....However as for not seeing colour (the check board is designed to deliberately trick the brain) not sure I would agree with the not seeing colour statement
The thing is, that we always see things on Earth under the same conditions in general with our star being a yellow dwarf G2V star.Colour of orange in the dark or under a blazing sun - it is the colour it is
Not really. I disagree with the guy on quora about all particles being "pure energy". Particles are excitations in quantum fields, yes, but that's not the same as "pure energy". The guy sounds reasonable enough that I think I could probably convince him of that with a brief conversation about it. It's not that he's exactly wrong, but he's using a metaphor without realising it. Like I said, it's a common mistake, and even physicists are prone to making it. To some extent, it doesn't matter if we're a little loose with the language, but when the question is this one it is actually important to get it right.
What I'm hearing is that you're not interested in whether you're right or wrong. As long as you walk away with your ego intact, you're content to be wrong. For you, this discussion ceased being about what is true some time ago. Now it's just about you trying to save face, at least as far as you're concerned.James, I'm not really interested in your deliberate act of confusion.
Here are some interesting answers which again validates the main point I have been making since the start of this...Pedant/Pedantic/Pedantry
http://scienceline.ucsb.edu/getkey.php?key=3971
That's a really great question. In fact this question caused a great debate among physicists during the time of Isaac Newton. Newton thought that light was a stream of little particles and other physicists such as Christian Huygens thought that the universe was filled with tiny particles called aether particles and that light was just a wave moving through the aether.
To make a long story short, it turns out they're both kind of wrong... and they're both kind of right. In some situations light sort of acts like a stream of particles and in others it acts sort of like a wave. Today many physicists (myself included) like to say that light is neither a particle or a wave... it's just light.
So, some might say that because light can carry energy from the sun to the earth it must be matter. Others might say that because you can't hold a lump of light in your hand light isn't matter. It all depends on what you mean by the word 'matter.' But the important thing to remember is that light doesn't care what you call it, it will still act the same way no matter what. That's why in physics we try not to worry too much about what things are called and focus on understanding how things actually behave.
Okay so far. I wrote the same thing, above.Answer 2:
"Both your class, and the entirety of science is having this debate. First, some precision. Photons are not in light, they are light. Light is made up of photons, so one photon is like one unit of light. Additionally, photons aren't really matter, although this depends on how you define things. Traditionally people say that for something to be called matter, it has to have mass and photons don't really have mass... although this also depends on how you define it.
Nup. Wrong! Back to school with you!I'll cut to then end, and then explain the controversy. Light is a form of electromagnetic radiation, which is a form of energy.
Sloppy. Yes, the energy in light comes in discrete amounts. Those amounts are associated with individual photons. The mistake comes when you say that the photons are the energy, or vice versa.This energy always comes in distinct units, which we call photons.
All fine, but irrelevant.In this way, light is like a particle, but it still doesn't have mass, so it's not really matter. The way these particles behave though, is very strange. Sometimes they behave more like a wave, like a ripple moving across a pond. Sometimes they behave more like actual solid objects, like bullets being shot from a gun. And the craziest thing is that whether they behave one way or the other depends largely on whether or not anyone is watching them at the time. I cannot explain this behavior... actually no one can. All we can do as scientists is observe that it is the case and describe it using mathematical laws. If you want to know more about how we know this to be true, there is a famous physicist by the name of Richard Feynman who explains it quite nicely....
Another error, even though it's a very common mistake. Energy and mass are not "perfectly equivalent". A certain amount of energy can be associated with a certain quantity of mass, but it is an error to think that mass is energy. If it was, we wouldn't need two different symbols with two different units, for starters. And besides, at this point the guy has forgotten about how he careful distinguished matter from light, earlier. He's muddled. He says light is energy. He says light is not matter. But then he says matter is energy, which would make matter and light the same thing. See? Muddled.Now I said that whether light has a mass or not depends on your definition, let me explain that. As I said, photons, and thus light, is energy. But there is a famous equation E=mc2 that tells us that the mass and energy are perfectly equivalent. E is energy, m is mass and c is the speed of light in a vacuum.
Nup. More sloppy thinking. You can, for instance, convert mass into photons, but that's not the same thing at all, since neither mass nor photons are energy.You can convert mass into energy and energy into mass.
From here on, it's just error compounding error.As a matter of fact, that's what the sun does every day, it converts some of its mass into energy, which we see as light.
I have no problem with anything there. Sounds like Dave is on the right track. Note that he nowhere says that photons are energy.As my time is short and precious, let's add some more while I have the time.....
http://curious.astro.cornell.edu/ab...ow-are-photons-created-and-destroyed-advanced
QUESTION:
I'm reading an excellent book by Kauffmann, Discovering The Universe, in which he describes when electron jump to a higher level or a lower level. If they go to a higher level they emit a photon. If they go to a lower level they absorb a photon.
It causes me to ask if photons exist as a seperate entity within all atoms or are they created at certain energy levels for the purpose of absorption, or emission, or do they exist omnipresently in the fabric of the universe? Anyway, where does the photon for absorbtion come from?
Hope this isn't too stupid a question.
ANSWER:
It certainly isn't a stupid question, and really cuts to the heart of the question of interpreting quantum mechanics.
The simplest answer is that when a photon is absorbed by an electron, it is completely destroyed. All its energy is imparted to the electron, which instantly jumps to a new energy level. The photon itself ceases to be. In the equations which govern this interaction, one side of the equation (for the initial state) has terms for both the electron and the photon, while the other side (representing the final state) has only one term: for the electron.
The opposite happens when an electron emits a photon. The photon is not selected from a "well" of photons living in the atom; it is created instantaneously out of the vacuum. The electron in the high energy level is instantly converted into a lower energy-level electron and a photon. There is no in-between state where the photon is being constructed. It instantly pops into existance.
So the question is: where does the photon come from?
Strangely, it doesn't seem to come from anywhere. The universe must put the extra energy somewhere, and because electrons in atoms are electromagnetic phenomena, a photon is born with the required energy. In a weak-force interaction, say the decay of a neutron, that energy goes into a neutrino particle which is also instantaneously created. Each force has its own carrier particles, and knows how to make them.
That's really all we can say about it. There are many interpretations of what this and other phenomena in quantum mechanics mean on a deeper level, and whole libraries worth of books which argue points of view on the matter. But my personal philosophy is that of the famous physicist Richard Feynman, who said: "Shut up and calculate."
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Dave Kornreich
Dave was the founder of Ask an Astronomer. He got his PhD from Cornell in 2001 and is now an assistant professor in the Department of Physics and Physical Science at Humboldt State University in California. There he runs his own version of Ask the Astronomer. He also helps us out with the odd cosmology question.
Some people just can't stand being corrected. I'm tempted, on the basis of this incivility, to just stop interacting with you. People aren't pricks just because they disagree with you. Grow up.I'm not a fucking idiot you condescending prick.
No. You can't create "stuff" from numbers.Why are you so convinced that it's wrong to say a photon is a form of energy, when clearly that's what electromagnetic energy "becomes", when as you say, an electron interacts with "the" electromagnetic field. So you might come to the conclusion that the photon is created out of the energy "in" the field.
A photon, as I and others have already explained many times, is an excitation of the electromagnetic field.But you don't really know do you? That's why it's so much easier for your small brain to handle properties--a photon has properties.
Where does it get them from, if photons are created and destroyed but energy isn't?
Another error. A photon is an excitation of the field; it is not the field itself. Your statement is equivalent to claiming that a water wave in a pond is the pond.Oh bullshit. That is so NOT it.
The photon does not travel "in the EM field"; it IS the EM field, you dick.
What is wrong is that whoever wrote that is hopelessly muddled about the difference between heat and radiation. Apart from that, the rest is sort of okay.What is wrong with these people--https://en.wikipedia.org/wiki/Electromagnetic_radiation
Infrared radiation in the spectral distribution of a black body is usually considered a form of heat, since it has an equivalent temperature and is associated with an entropy change per unit of thermal energy. However, "heat" is a technical term in physics and thermodynamics and is often confused with thermal energy. Any type of electromagnetic energy can be transformed into thermal energy in interaction with matter. Thus, any electromagnetic radiation can "heat" (in the sense of increase the thermal energy temperature of) a material, when it is absorbed.[38]
Oh well, indeed. Maybe somebody will help correct them, like I'm helping by correcting you. Maybe you can take what you learn here and spread the knowledge around. Maybe together we can correct the internet, bit by bit.Don't they realise James R and exchemist, here at sciforums, are sure that EM radiation can't be a form of heat? That would mean having to also accept the EM radiation is a form of energy (although that seems to depend on what is meant by "heat").
Oh well.
This is ambiguous. On the one hand, it can be read as saying that particles are a form of energy and there are other forms. On the other hand, Schrodinger might just be saying that energy can be emitted from the nucleus by many different processes. It's not clear which meaning he meant. If it was the former, then he was wrong; if the latter, then no problem.Within one tremendously fertile decade at the turn of the century came the discoveries of X-rays, of electrons, of the emission of streams of particles and other forms of energy from the atomic nucleus by radioactive decay . . .
It's an understandable mistake he is making here - one that many physicists make. In practice, it doesn't make much difference if you pretend this is true. But, technically, it's wrong. Energy and mass are not one and the same. You can't make stuff from numbers.Five years later Einstein told us that energy has mass and mass is energy; in other words they are one and the same
Fine.Each small system--atom or molecule--can only harbor discrete energy quantities. . . .
This is okay, but only if the word "radiation quantum" is understood to mean a discrete quantity of energy associated with a photon ("radiation"). An erroneous reading would be to interpret this as saying that energy (numbers) can somehow turn into photons (stuff).In transition from a higher to a lower "energy level" [the system] emits the excess energy as a radiation quantum of definite wavelength . . .
What's confusing you?Ok, EM radiation can't be energy. So confusingly, this radiation carries energy.
What do you find problematic about any of that? You're dismissing it, but you're not saying why.So when an electron emits a photon, the photon isn't energy, but rather a thing that carries energy and momentum away from the electron. But this energy and momentum depends on the motion of the electron because it can be moving.
Are you telling me that you don't care how many good arguments I make, you're unwilling to believe me because I disagree with some "big name" authorities about certain subtle points?I'm still stuck on the idea that there are thousands of books and articles in the world, many of them saying something that James R informs me is wrong. Saying a photon is a form of energy like many physicists do (this includes Schrodinger and Einstein), is wrong; it's misleading . . .
Okay. That's all good. What's the relevance?What "something else"? . An electron spontaneously emits radiation (in discrete amounts), when it accelerates. Accelerating an electron means it has to interact with an electric field (or a magnetic field). In the first case the electron accelerates linearly; in the second case it follows a curve.
Electrons accelerating in a strong magnetic field generate synchrotron radiation.
LEDs emit radiation which is monochromatic, because electrons in the LED accelerate (not very far) in an applied (constant) electric field--the "something else" . . .
Yes. I agree with all that.A photon is energy, but when you see light you don't see energy. Seeing light means you interact with photons and they exchange momentum with electrons.
OK? That's a fairly standard explanation; energy can't be measured but it can be calculated.
I haven't talked about most modern textbooks. I believe that so far we have discussed what one textbook says - one that you happen to have at hand. Nor have I made any comments about a university education in physics.But keep telling yourself that most modern textbooks are wrong, that a university education in physics won't be helpful.
I don't know where you're getting this stuff from. Not from anything I've said. How can we hope to identify errors in the literature if we don't consult it?No point in consulting any literature at all, really.
I wouldn't put all the blame on them. People manage to mislead themselves. Also, this stuff isn't necessarily taught. People (even teachers) aren't always as careful as they should be in how they use the language, and as a result their students sometimes take away the wrong ideas.Considering Einstein, Schrodinger, probably Maxwell too, were all confused about it and so managed to mislead a lot of people . . .
Electromagnetic energy doesn't have to be energy in order to have an energy associated with it. Energy is useful precisely because it's a good accounting system.I'm waiting to see if James R or exchemist can explain how the power output of a radio antenna is calculated, given that electromagnetic radiation isn't a form of energy.
I've already told you, but maybe I wasn't clear.I'd also like an explanation of what both of them think a "form" of energy actually is.