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Quantum Mechanics

Quantum Mechanics is the branch of physics that deals with the study of the structure and behavior of atoms and molecules. It is primarily based on Max Planck's Quantum theory, which incorporates Heisenberg's uncertainly principle and the de Broglie wavelength to establish the wave-particle duality on which Schrodinger's equation is based.

916 Questions

What is the difference between relativistic and non-relativistic wave equation?

The relativistic wave equation, such as the Klein-Gordon equation or the Dirac equation, takes into account special relativity effects such as time dilation and length contraction. On the other hand, the non-relativistic wave equation, such as the Schrödinger equation, does not include these special relativity effects and is valid for particles moving at much slower speeds compared to the speed of light.

What is the gauss theory?

The Gauss theory, also known as Gauss's law, is a fundamental principle in physics that relates the distribution of electric charge to the resulting electric field. It states that the total electric flux through a closed surface is proportional to the total electric charge enclosed by that surface, divided by a constant. This law is a powerful tool for understanding the behavior of electric fields and is used extensively in electromagnetism.

Why time isn't an operator in quantum mechanics?

Associated with each measurable parameter in a physical system is a quantum mechanical operator. Now although not explicitly a time operator the Hamiltonian operator generates the time evolution of the wavefunction in the form H*(Psi)=i*hbar(d/dt)*(Psi), where Psi is a function of both space and time.

Also I don't believe that in the formulation of quantum mechanics (QM) time appears as a parameter, not as a dynamical variable. Also, if time were an operator what would be the eigenvalues and eigenvectors of such an operator?

Note:A dynamical time operator has been proposed in relativistic quantum mechanics.

A paper I found on the topic is;

Zhi-Yong Wang and Cai-Dong Xiong , "Relativistic free-motion time-of-arrival", J. Phys. A: Math. Theor. 40 1987 - 1905(2007)

What is quantum of electric charge?

The quantum of electric charge is the smallest unit of electric charge, carried by a single electron or proton. It is approximately equal to 1.602 x 10^-19 coulombs. This value determines how charges are quantized in nature.

What are the benefits of quantum mechanics over classical mechanics?

Well, that depends on what you meant by "benefits". Either way, both of them have their limitations. Classical mechanics can not be used to accurately describe an atom. Just as quantum mechanics would be useless if you were asked to find the terminal velocity of a baseball. Both areas have give us a plethora of inventions and technologies that would not have existed otherwise. Now in terms of learning the topics, quantum mechanics is deemed by some to be more interesting because of its mystery (probabilistic predictions) versus classical mechanic's seemingly dry Hamiltonians and Lagranians. Both topics are very powerful tools that are used to solve complicated problems, and one is not really better than the other but I believe that neither is complete. I hope that helped.

Quantum mechanics and quantum physics apply to?

the study of the very small scale of particles, such as atoms and subatomic particles. Quantum mechanics deals with the fundamental behavior of these particles, including phenomena like superposition and entanglement, while quantum physics encompasses the broader study of quantum phenomena and their applications.

Why quantum mechanics is not suitable for large systems?

Quantum mechanics is usually not suitable for large systems because the interactions between particles become too complex to model accurately. Quantum mechanics relies on delicate entanglement between particles, which becomes increasingly difficult to maintain as the system size grows. Additionally, the computational resources required to simulate large quantum systems increase exponentially, making it impractical for most applications.

What is study of velocity speed and acceleration called?

The study of velocity, speed, and acceleration is called kinematics. Kinematics is a branch of physics that deals with the motion of objects without considering the forces causing the motion.

In young's double slit experiment two slits are made 1mm apart and the screen is placed 1m awaywhat is the fringe separation when blue light of 500cm is used?

The fringe separation can be calculated using the formula: fringe separation = wavelength * distance to screen / distance between slits. For blue light with a wavelength of 500 nm and a distance of 1m to the screen and 1mm between the slits (1mm = 0.1 cm), the fringe separation comes out to be 0.05 mm or 50 micrometers.

What is the smallest particle of matter found till date?

I believe the smallest particle known of at present is the neutrino (which translates to "small neutral one")

They have minimal interaction with other particles, with no electric charge, and a "small but non-zero mass." According to wikipedia, the mass is believed to be less than 0.3 electronvolt. An electronvolt is a unit of energy that can be used as a unit of mass in particle theory due to energy-mass equivalence (e=mc^2). By comparison, an electron weighs 511000 electronvolts, and the mass of an electron volt in conventional units is determined by the following conversion factor: 1 000 000 000 V/c2 = 1.783 × 10−27 kg

Source: wikipedia articles on neutrinos and electronvolts.

Is Quantum Mechanics more important than Relativity?

Quantum mechanics and relativity are both parts of the same puzzle: how the universe works. They are both equally important, because they both explain things that are not explained by classical physics.

Physical significance of green function in quantum mechanics?

There are two parts to this. First is, "What is the physical significance of a wave function?" Secondly, "Why do we normalize it?"

To address the first:
In the Wave Formulation of quantum mechanics the wave function describes the state of a system by way of probabilities. Within a wave function all 'knowable' (observable) information is contained, (e.g. position (x), momentum (p), energy (E), ...). Connected to each observable there is a corresponding operator [for momentum: p=-i(hbar)(d/dx)]. When the operator operates onto the wave function it extracts the desired information from it. This information is called the eigenvalue of the observable... This can get lengthy so I'll just leave it there. For more information I suggest reading David Griffith's "Introduction to Quantum Mechanics". A math knowledge of Calculus II should suffice.

To address the second:
Normalization is simply a tool such that since the probability of finding a particle in the range of +/- (infinity) is 100% then by normalizing the wave function we get rid of the terms that muddy up the answer the probability.
An un-normalized wave function is perfectly fine. It has only been adopted by convention to normalize a wave function.

ex. un-normalized wave function (psi is defined as my wave function)
- The integral from minus infinity to positive infinity of |psi|^2 dx = 2pi

ex. normalized wavefunction
- The integral from minus infinity to positive infinity of |psi|^2 dx = 1

Suppose an electron is accelerated from rest through a potential difference of 150kV. What wavelength shoud it have?

The wavelength of the electron can be calculated using the de Broglie wavelength formula, which is λ = h/p, where λ is the wavelength, h is the Planck constant, and p is the momentum of the electron. The momentum of the electron can be calculated using the relation p = sqrt(2mE), where m is the mass of the electron and E is the energy gained by the electron from the potential difference. By substituting the given values into these equations, you can calculate the wavelength of the electron.

It takes 6.08 multiplied by 10-19 J of energy to remove one electron from a certain metal surface What is the maximum wavelength of light capable of causing this effect?

best way to write above question is:

Work function = 6.08*10^-19J This is energy Min required to free one electron.

what max wavelength is requred to cause this event?

remember wavlength inversely proportional to energy of photon via planks constant h

hence E = hV but E = hc / (wavelength)

where

E = energy photon

V = frequency of photon

h = planks constant = 6.626068 × 10-34 m2 kg / s

now, because Min energy is proportional to max wavelength, which is related to frequency:

V = E/h = (6.08*10^-19J) / ( 6.626068 × 10-34 m2 kg / s)

= 9.176 * 10^14hz

now C = V*(wavelength)

so (wavelength) = (3*10^8m/s) / (9.176*10^14hz) =

= 3.27*10^-7 meters

between 0.7 and 300 micrometres is infra-red, but this is 0.327 micrometers!! This seems like a very large wavelength, and therefore low energy value.

What is the equation for the amount of energy to move an atom?

The equation for the amount of energy to move an atom is given by the formula E = F × d, where E is the energy, F is the force, and d is the distance the atom moves. This equation represents the work done in moving the atom.

How does the Higgs work in the Mexican Hat potential?

The Higgs field has a non-trivial self-interaction, which leads to spontaneous symmetry breaking: in the lowest energy state the symmetry of the potential (which includes the gauge symmetry) is broken by the condensate.

In the simplest example, the spontaneously broken field is described by a scalar field theory. In physics, one way of seeing spontaneous symmetry breaking is through the use of Lagrangians. Lagrangians, which essentially dictate how a system will behave, can be defined in potential terms:

L = du(f)du(f) - V(f).

It is in this potential term V(f) that the action of symmetry breaking occurs. The potential graph of this function has the look and appearance of a Mexican hat.

Why did Elmer Samuel Imes apply infrared spectroscopy to the quantum theory?

Elmer Samuel Imes applied infrared spectroscopy to the quantum theory to investigate the interactions of molecules with electromagnetic radiation and to provide experimental confirmation of quantum theory predictions. By studying the absorption and emission of infrared radiation by molecules, Imes was able to demonstrate the quantization of energy levels in molecules, supporting the principles of quantum mechanics.

How can a photon have frequency?

A photon behaves both as a wave and a particle. The frequency of a photon is related to its energy by the equation E = hf, where E is energy, h is Planck's constant, and f is frequency. So, the frequency of a photon is a characteristic of its wave-like nature.

How can a photon have color?

A photon's color is determined by its wavelength, which corresponds to a specific color in the visible spectrum. A photon of shorter wavelength appears bluer while a longer wavelength appears redder. The perception of color in photons is a result of how our eyes detect and interpret different wavelengths of light.

What is the wave function of 2 electron system of spin one state?

The wave function of a two-electron system with total spin one can be expressed using the symmetric spin wave function, taking into account both spatial and spin components. This wave function should satisfy the Pauli exclusion principle and be antisymmetric under exchange of electron coordinates.

Why does the temperature of a blackhole increases with decrease in volume or size?

First, you got to understand something. A black hole is just as a block of ice. The smaller it is the faster it melts. So speaking scientifically the black hole releases radiation relatively faster when its smaller than when it's bigger, which heats up the dead star. For that reason the black holes evaporate over a long time

What is the input quantity in quantum mechanics?

In quantum mechanics, the input quantity is the state of a quantum system, which describes all possible information about the system's physical properties at a given time. This state can be represented by a wave function, which contains information about the probabilities of different outcomes when the system is measured. The state evolves in time according to the Schrödinger equation, which describes how the system changes over time.

What are the eigenfunctions of the Laplace operator in 1D?

In general, the Laplace operator in n dimensions is

∇2 = (∂/∂x1)2 + (∂/∂x2)2 + ... + (∂/∂xn)2,

and the eigenfunctions are the solutions f(x1, x2, ..., xn) of the partial differential equation:

∇2f = -λf,

where the eigenvalues -λ are to be determined. Often, the set of solutions will be constrained by given boundary conditions (which limits the possible values of λ), but for the purposes of this question that does not matter.

In one dimension this gives a simple linear differential equation with constant coefficients:

d2f/dx2 = -λf

which may be solved using standard, elementary techniques. For λ > 0 the solutions may be written:

f(x) = A cos((√λ) x) + B sin((√λ) x)

and for λ < 0:

f(x) = A exp((√-λ) x) + B exp(-(√-λ) x)

where in each case A and B are arbitrary constants. Using Euler's formula

exp(ia) = cos(a) + i sin(a)

the solutions in both cases can be written as linear combinations of the exponential functions exp((±iλ) x).

In the case that λ = 0, the solutions are straight lines:

f(x) = Ax + B.

How do you find Polar moment of inertia of a 3d rigid body?

The polar moment of inertia of a 3D rigid body can be found by integrating the square of the distance from the axis of rotation for all the infinitesimally small elements of mass in the body. This integral takes into account both the area moment of inertia and the mass distribution of the body. The final result is a measure of the body's resistance to torsional deformation.

What is planks quantum hypothesis?

That light comes in indivisible chunks (he called them "quanta" but the present term is "photons") and that the energy of each such quanta is equal to the frequency of that light times a constant (now called Planck's Constant).

When Max Planck first proposed this idea in 1900, he only noted it as a mathematical curiosity that would permit a solution to the spectrum of black-body radiation. In other words, he didn't assert that it was actual description of reality. In 1905, Einstein noted that this same assumption would fully explain the photoelectric effect.