TrueTears question thread

[kamil9876]

Well I don't know how much is expected in the current course when it comes to wave optics. But I can tell you that the position(indicated by angle) of the first dark band is an indication of how much has been diffracted. And this position is indicated by that ratio(bigger ratio ==>bigger ==> bigger theta ==> more spread out ==> more diffraction(greater extent of diffraction)). Hence the questions of the sort "is the diffraction significant" just need that ratio. All I did was just provide an explanatiotn of why this ratio is an indication of it, since you like these sorts of explanations. And if you're after the band(if it's still on course) then yeah, just the general formula will do.

[TrueTears]

Ahh okay thanks kamil, so how would you answer the question before?

"what is the ratio of if the point on the wall/plate  is a dark band occurring at n = 2.5 and the central maximum is n = 0."

[NE2000]

haha my relativistic dynamics are piss poor:

But i can say that p=mv is not momentum when v is near c, let alone equal to it:

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/relmom.html

Notice on the bottom how it says:



and so p=E/c at the limit. and use

Actually, it even says on the bottom:

with the limiting case applying for the momentum of a photon.

lol this bothered me for a bit as well so thanks for that...that and the idea that I have a de Broglie wavelength when moving

This may seem a bit superficial but sometimes I like drawing diagrams to confirm concepts and I was wondering how people picture a photon in their mind. I was sort of getting an idea of it and then Taylor's experiment for the diffraction of individual photons threw me off. So just wondering how people visualise it.

[TrueTears]

Yeah the Taylor's experiment with the diffracting photon, you will need to get into quantum mechanics to understand that; where wave/particle nature of light/matter is unified. For now I just think of photons as a discrete amount of energy, kind of like a ball of energy.

[NE2000]

Ahh okay thanks kamil, so how would you answer the question before?

"what is the ratio of if the point on the wall/plate  is a dark band occurring at n = 2.5 and the central maximum is n = 0."

Yeah I'm pretty sure the current course just requires us to determine whether the diffraction will be significant or not by looking at the ratio. Maybe it's just my lack of knowledge at this point but it seems like there should be more information... :S

[NE2000]

Yeah the Taylor's experiment with the diffracting photon, you will need to get into quantum mechanics to understand that; where wave/particle nature of light/matter is unified. For now I just think of photons as a discrete amount of energy, kind of like a ball of energy.

Yeah but how does a ball of energy diffract...

btw, do you use Jacaranda? It's just that from what I remember Jacaranda said something similar about the wave and particle theories on light and matter being "unified successfully" in quantum mechanics...leaving us in suspense (clearly a ploy to get more people to do physics at uni)

[TrueTears]

Yeah the Taylor's experiment with the diffracting photon, you will need to get into quantum mechanics to understand that; where wave/particle nature of light/matter is unified. For now I just think of photons as a discrete amount of energy, kind of like a ball of energy.

Yeah but how does a ball of energy diffract...

btw, do you use Jacaranda? It's just that from what I remember Jacaranda said something similar about the wave and particle theories on light and matter being "unified successfully" in quantum mechanics...leaving us in suspense (clearly a ploy to get more people to do physics at uni)

Yeap, that's right.

And exactly what I was thinking, how can a ball of energy diffract? Asked my teacher a few days ago, he said he doesn't even know.

[NE2000]

Yeah the Taylor's experiment with the diffracting photon, you will need to get into quantum mechanics to understand that; where wave/particle nature of light/matter is unified. For now I just think of photons as a discrete amount of energy, kind of like a ball of energy.

Yeah but how does a ball of energy diffract...

btw, do you use Jacaranda? It's just that from what I remember Jacaranda said something similar about the wave and particle theories on light and matter being "unified successfully" in quantum mechanics...leaving us in suspense (clearly a ploy to get more people to do physics at uni)

Yeap, that's right.

And exactly what I was thinking, how can a ball of energy diffract? Asked my teacher a few days ago, he said he doesn't even know.

Doesn't Scotch have this awesome physics teacher that inventing a diamond-making machine?

[TrueTears]

Yeah [he was year 11 teacher, to be honest, he was pretty crap, he is definitely smart but has no idea how to teach.]

[rhjc.1991]

Yeah [he was year 11 teacher, to be honest, he was pretty crap, he is definitely smart but has no idea how to teach.]

Ah why does that line sound SO familar? lol

[NE2000]

Yeah [he was year 11 teacher, to be honest, he was pretty crap, he is definitely smart but has no idea how to teach.]

Ah why does that line sound SO familar? lol

hmmm......why?? [sorry]

[rhjc.1991]

Yeah [he was year 11 teacher, to be honest, he was pretty crap, he is definitely smart but has no idea how to teach.]

Ah why does that line sound SO familar? lol

I meant that I know/heard of so many teachers like that.
hmmm......why?? [sorry]

[TrueTears]

Ahh so how would you answer the question before?

"what is the ratio of if the point on the wall/plate  is a dark band occurring at n = 2.5 and the central maximum is n = 0."

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A dark region in a 2-slit interference pattern is caused because
I choose "The photons or particles annihilate each other at that point"
but answer is "the photons or particles simply do not travel to that point"

and

A question says
light from the door to a very hot blast furnace
what describes the spectrum?
answer is "The spectrum is continuous: there is a spread of wavelength from the infra red right through to the visible range"


Why??

Thanks!

[Mao]

Yeah the Taylor's experiment with the diffracting photon, you will need to get into quantum mechanics to understand that; where wave/particle nature of light/matter is unified. For now I just think of photons as a discrete amount of energy, kind of like a ball of energy.

Yeah but how does a ball of energy diffract...

btw, do you use Jacaranda? It's just that from what I remember Jacaranda said something similar about the wave and particle theories on light and matter being "unified successfully" in quantum mechanics...leaving us in suspense (clearly a ploy to get more people to do physics at uni)

Yeap, that's right.

And exactly what I was thinking, how can a ball of energy diffract? Asked my teacher a few days ago, he said he doesn't even know.

A ball of energy does not diffract. But because the ball of energy also have a wave duality, due to some quantum stuff or other diffraction occurs no matter how you look at it.


A dark region in a 2-slit interference pattern is caused because
I choose "The photons or particles annihilate each other at that point"
but answer is "the photons or particles simply do not travel to that point"

A dark band exists because impact density there is zero. When you think about it in terms of waves, the superposition at that point gives you a flat line. A flat line (no displacement) is a wave with no energy, and since each photon has some energy, there must be no photons.

light from the door to a very hot blast furnace
what describes the spectrum?
answer is "The spectrum is continuous: there is a spread of wavelength from the infra red right through to the visible range"

In this case, we're talking about thermal emission. In heat, electrons accelerate/decelerate due to collisions with other particles, and in the process, release energy. Hence the light emitted is not a distinct set of frequencies, but rather a bunch of 'random' values that forms a continuous spectrum with peak related to temperature. Research 'black body radiation' for more.

[TrueTears]

Thank you Mao! I get it now, kekekeke xie xie !