# Tag Info

1

In thermodynamics, a closed system is a system which cannot exchange matter with the environment. An isolated system cannot exchange matter nor energy with the environment. So, an isolated system is also closed, but the reverse is not true.

3

An isolated system can radiate energy/momentum/angular momentum away, but isn't externally influenced. A closed system is an isolated system that also has fixed net energy, momentum, and angular momentum.

0

Fluorescence can occur at any wavelength, it is the transition between states of the same spin, e.g. most always excited singlet ($S_1$) to ground state singlet ($S_0$) which both have spin = 0 (and spin multiplicity 1). This can occur over a wide range of wavelengths; bacteriochlorophyll emits in the near infra red at approx 850 to 900 nm as it absorbs at a ...

2

As far as the second part of your question is concerned you can directly see the image improvement with squinting. If you have a DSLR with aperture settings you keep the camera slightly defocused and now reduce the aperture you will see that the image is becoming sharper. However at the same time the image will become darker because you are collecting less ...

1

EDIT Please see the comments following my answer, regarding the paragraph below , as it is incorrect. Strabismus is the clinical name for squinting. The squint is simply compression of the eye muscles to compensate for problems with focusing and / or astigmatism. END EDIT In a somewhat similiar way, telescopes using adaptive optics can distort the ...

0

Decay width ($\Gamma=\frac{1}{\tau}$) which is a measure of the probability of a specific decay process occurring within a given amount of time in the parent particle’s rest frame. The decay width $\Gamma$ of particle is directly related to its decay lifetime: the faster the particle decays, the larger its decay width. Since the dimension of $\Gamma$ is ...

6

You're having trouble telling the difference between the two because, as for many natural language words, I don't think there is a clearly defined difference and the difference arises from natural usage (as with the difference between "fruits" and "vegetables" in English). The following is my understanding of the difference. There is a well defined ...

0

Quadrature has a very clear and precise meaning in Quantum Mechanis. Some quantities don't commute, i.e., you cannot measure both of them with unlimeted precision. This is related to Heisenbeg unsertainty. Let's put this two variables in the Cartesian plan and call this observables as X and Y.. if X is position then Y is momentum. If X is electric field ...

2

In watchmaker lingo, a "retrograde" watch is a watch that has a hand on it (usually to tell you the day or date) that will advance along and then at the end of its "cycle" will snap backwards to its original position -- rather than loop around the way the hour, minute, and second hands do. This has nothing to do with the "retrograde motion" discussed in ...

-1

Transparent object allow light to pass throught them and we can see throught these objects clearly translucent object allow light to pass through them partially.

4

According to the Particle Data Group [1], Mesons are [strongly interacting particles that] have baryon number $\mathcal{B}=0$. In the quark model, they are $q\bar{q}'$ bound states of quark $q$ and antiquark $\bar{q}'$. This definition has two sentences, which in fact are somewhat different. The second one defines the quark-model mesons, that you're ...

0

I think the best way to think of it is as follows.(It's not too different from what everyone has said, but may be put into better perspective). Choosing a frame of reference is a completely different job than setting up of coordinates. To observe an event in spacetime you must belong to some frame of reference(or equivalently, you create a frame of ...

1

The simplest way I can think of correctly defining quantum physics is that it is the combination of our best and most correct theories of physics that does not include General Relativity. There are two relevant and important classes of physics for this explanation: classical physics and quantum physics. Physicists are people too. If we can achieve our ...

0

The QM notion of a "force" is highly technical jargon that doesn't match up with how the word force is used in the world at large. Basically, the notion of a "force" in QM is defined to be an interaction mediated by force carrier particles and therefore the exchange-interaction is arbitrarily defined not to be a force. Likewise, gravity is not a "force" ...

1

I want to add an answer which I think supplements some of the other comments. @lemon notes that "gravity" refers to the pull towards the Earth while "gravitation" is more general, but notes that this is archaic. In fact, it is a very old term and the history is interesting, so take this as a "history of science" type answer. Disclaimer that all of what I ...

0

That's incorrect definition propagated by text books for simplicity sake. Gravity should always be defined as a force that attracts a body towards another physical body with mass. For simplicity sake, gravity is taught as the force with which Earth pulls a body.

5

Let me preface by saying that "coupling" is a favorite physicist word that is perhaps best described linguistically than rigorously; it's deployed in a few different situations. In general, we say that a coupling exists in quantum mechanics if the evolution of one part of the system depends on another quantity, which could be either classical or quantum. I'...

-3

I think Entanglement may answer your question. Two systems are said to be entangled(coupled) if we cannot assign an independent and separate wavefunctions for each system, instead we define a composite system which is simply the tensor product of the original constitutes. To be precise, in the general case the wavefunction description of any quantum system ...

Top 50 recent answers are included