# All Questions

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### Can we apply de Broglie's relations to sound waves?

Can we apply the de Broglie relations to a sound waves ? Is it possible? if yes how do you do that? what would be the mass(m) in the equation?
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### Clarification on measurement in QM

Supppose we are given a quantum state that isn't pure state, such that it is a linear combination of the eigenstates of a Hermitian operator $\hat O$. $$|\psi\rangle=N\sum \alpha_i |i\rangle$$ where ...
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### What are the concepts and explanation to these questions?

I'm looking through my old quiz, and I don't understand these concepts. Could someone explain the concepts to me so that I can answer these questions? What topics should I look over, specifically? 1) ...
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### Quantum Field Theory and Hilbert space dimensionality

Much (All?) of quantum theory can be done in separable Hilbert spaces with a countable basis. How about quantum field theory? Is it “quite happy” (mathematically consistent) if everything is ...
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### Calculate the distance between two points from iPhone Camera

I want to calculate the distance between two point from iPhone camera. Suppose I am standing with my iPhone (with camera on) 10 feet far from the object. So my two objects are 10 feet far from me ...
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### Molecular dynamics simulation: fluctuating dipole model implementation

I'm conducting a molecular dynamics simulation for silica. Some time ago I turned to the fluctuating dipole model, and after a much efforts I'm still having problems implementing it. In short, all ...
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### Can one define a “particle” as space-localized object in quantum field theory?

In Peskin and Schroeder, while discussing creation and annihilation operators for a Klein-Gordon field (p.22), the authors say, as we all know the creation operator a_p^{dagger} acts on vacuum to ...
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### $SiO_2$ PVD deposition to HDPE (plastic)

Is it possible to deposit $SiO_2$ onto HDPE plastic parts (Fresnal Lens)? Will the deposition disrupt infra transmission?
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### Why should a battery not give current in order to define EMF?

Emf is the "potential difference across the terminals of a battery when it is giving no current to the circuit." What does "when it is giving no current mean." Will the PD across the terminals of ...
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### Precise statement of Mermin–Wagner theorem

Roughly speaking, Mermin-Wagner theorem states that continuous symmetries cannot be spontaneously broken at finite temperature in systems with sufficiently short-range interactions in dimensions ...
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### Hilbert space of a free particle: Countable or Uncountable?

This is obviously a follow on question to Hilbert space of harmonic oscillator: Countable vs uncountable? So I thought that the Hilbert space of a bound electron is countable, but the Hilbert space ...
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### Trying to understand mixed states

I took a basic quantum chemistry course (McQuarrie's "Quantum Chemistry"), but it never dealt with mixed states -- only pure states (or if it did, we never got to it in class). So I'm trying to ...
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### How does optical phase modulation produce photons with different frequencies?

The classical description of electro-optic modulators is an index of refraction that depends on the applied voltage. For example, for a sine modulation $\sin(\Omega t)$, a monochromatic laser of ...
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### how many qubit we are need to store “16”?

classical computers store information in bits which can either be 0 or 1, but in quantum computer the qubit can store 0 , 1 or a state that is the superposition of these two states so how this ...
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### Why doesn't this equation for orbital motion change with position in the orbit?

The question and answer are on pg.8-10 of this PDF: At first, I went through it, thinking nothing of it. But then, I wondered: "What if we picked a final state in which the space junk was NOT at ...
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### What is the difference between material fatigue test with 1 sec cycle and 1 hour cycle?

Assume I have two piece of metal. I want to test the material fatigue (e.g. How many cycles can the material stand before break). One of them I apply tension force every 1 second. The other one I ...
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### Doubt on the analysis of $RC$ circuit

I'm studying $RC$ circuits and I'm in doubt on how to deal with one kind of situation. Well, first when we have simply a circuit with just one resistor and one capacitor in series, or a circuit that ...
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### The Sine pattern of variation [closed]

I'm trying to fully understand sin and cos as a certain pattern of variation, a particular variation that start's to decelerate smoothly towards the peaks and starts to accelerate abruptly towards the ...
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### Electric and Magnetic Field [closed]

Accelerated charges directed into regions between parallel plates with E and B fields – how are the charges deflected?
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### Magnetic Force on a Loop and number of turns

Suppose we have a rectangular current-carrying loop with current $i$, then we know that the magnetic force on each side can be found as: $$F=iL\times B$$ Where $L$ is the vector in the direction of ...
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### Electric Field and Electric Potential [closed]

How can electric field and electric potential function for charged conducting and uniformly charged non-conducting spheres?
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### Wave function interpretation $y(x,t) = (0.35m)\sin(10\pi t-3\pi x + \frac\pi{4})$

Wave function interpretation $y(x,t) = (0.35m)\sin(10\pi t-3\pi x + \frac\pi{4})$ I used to deal with function with one variable And now theres are two, how can I interpret them? Is $10\pi$ still ...
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### A double-sided lever and multiple forces

Assume a double-sided lever where the left arm has a length of a and the right arm has a length of b + c. Please refer to this ...
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### Difference between velocity vectors, relative speed

Consider two particles moving in the same direction instantaneously but one of them follows a circular path and one follows a straight path. If I adopt a rotating frame of reference in which the ...
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### How does the volume change affect an adiabatic process?

A gas consisting of rigid diatomic molecules was initially under standard conditions. Then the gas was compressed adiabatically, 5 times the original volume. Find the mean KE of rotating molecules ...
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### Historical aspect of wave theory of light

Huygens thought light as a wave. Wave is a propagation of physical disturbance. We now know that light is electromagnetic field. Electric and magnetic field fluctuates here. What Huygens really ...
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### Dividing values with units

I'm reading about the subject of heat in a basic physics book. If I am not mistaken the formula to work out how much energy is required to increase the temperature of water is ...
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### What really is the Magnetic Force on a wire?

I have a doubt regarding the significance of a force on a wire. Well, first of all, I know that if I have a particle and if there are several forces acting over it, then we can compute one total force ...
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### Derivative of $\epsilon$ in lennard jones equation

I just want to calculate the derivative of epsilon for the following Lennard Jones equation: LJ = $4\sqrt{\epsilon_{ii} \epsilon_{jj}}$ $[(\sigma/ r)^{12}-(\sigma/r)^{6}]$ with respect to ...
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### How does relativity explain gravity, without assuming gravity [duplicate]

I have seen the "objects pull down on space-time" explanations, but they assume a "pull down" force themselves. Could anyone explain the space-time explanation without assuming gravity in the first ...
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### Interpretation of de Broglie wave

Until what point can the de Broglie wave be thought as a real wave? I mean, is it made of something? What amplitude does it have? Is it a sine wave? How can it be related to the wavefunction of the ...