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.

3,233 Questions
Quantum Mechanics

Why are leptons divided into families?

Leptons are divided into three families with 4 particles (2 particles, plus their two anti-particles) in each family. In the electron family we have the electron, positron, electron neutrino and electron anti-neutrino. Each family has a higher mass than the one before it so the tauon is heavier than the muon which is heavier than the electron. The physical reason for there being three families is completely unknown and will probably win you a Nobel prize if you can figure it out!

Nuclear Physics
Quantum Mechanics

What is mutual annihilation?

I am not the expert in the field of physics. But I also have not lost my common sense. When electron and positron collide with each other, you get two gamma rays. My esteemed colleague Quirkyquantummechanic has said that the particle and antiparticle are completely converted into energy. Then does this formation of the energy match with the famous equation of the Einstein? The equation goes as E = m c square. Here c is the speed of light. Speed of light is fairly high. Speed of light is roughly 300,000,000 m/s. The square of this number is 90,000,000,000,000,000. As per the theory of my colleague, you get only one gamma ray each from the entire mass of the electron or the positron. It fallows that from the mass of one electron, you get one gamma ray only and from the mass of positron, you get another gamma ray only. Then it is logical that you get one electron from one gamma ray and one positron from another gamma ray. ( The reverse of the process of annihilation.) This is not correct. If you put the mass of the electron and positron, in the equation of the Einstein, you will get much higher energy, than what my colleague has mentioned. (He has mentioned that you will get pair of gamma rays.) This is called as 'emotional' involvement into what you 'believe' in. Science has nothing to do with your 'emotions' and 'beliefs'. You have to explain every thing with logic. Here goes the explanation for the same. It is the 'kinetic' energy of of the electron and positron, that is left as the pair of gamma rays. The electron and positron vanish into 'nothing'. This is one of the greatest invention of the modern time. From particle (electron) you get gamma ray. It fallows that from antiparticle (positron), you get anti-gamma ray. When proton collide with anti-proton, you get many gamma rays, electrons and positrons and neutrinos. Here the kinetic energy has to be much more than electron positron pair. As the mass of the particles is much larger. There has to be 'equal' number of electrons and positrons get generated in the process. They can in turn again get annihilated into nothing and pairs of gamma and anti-gamma rays. The best way to study the annihilation is to study annihilation between neutron and anti-neutron. Here the element of electrical charge is not there. Here you will find that there is complete destruction of the mass into number of electrons and positrons and number of gamma rays. These electrons and positrons will annihilate each other to give you more pairs of gamma rays. So you will get complete destruction of the particle and anti-particle into nothing and only kinetic energy remains there as gamma and anti-gamma rays. If neutrinos are released, then half of them has to be anti-neutrinos. As per Einsteins equation you have E = m c square. if you multiply the equation by minus one, what you get is : minus E = Minus m c square. If you denote the particles as 'm' in the above equation, then you have to denote anti-particle as 'minus m'. It fallows that from anti-particle, you get anti-energy. Even if the 'slightest' mass can be destructed into nothing, then 'all' the mass can be destructed into nothing. This explains the the theory of origin of matter and anti-matter from nothing. Any thing of this sort is bound to generate the emotional reaction. But then the truth only prevails. Here goes the link to the theory. http://www.answers.com/Q/What_is_the_theory_of_creation_of_the_matter_and_anti_matter_from_nothing

Quantum Mechanics

What is the basic principle of microwave spectroscopy?

atoms vibrate at particular frequencies, depending on their energy. If the energy of a particular atom has a vibration frequency in the microwave domain then you can know it's energy by measuring it's frequency by, Energy = plank's constant (times) frequency => E=h*f

In spectroscopy matter interacts with electromagnetic waves which are classified on the basis of their frequencies. e,g ultraviolet, infra red, x rays, radio waves and microwaves. Each category brings out specific changes in the molecule like in UV electronic transitions are observed and in IR vibrational changes are observed. These changes are observed when the energy requirement of the compound matches with the energy of the wave which can be calculated by the formula mentioned above.

Atoms and Atomic Structure
Quantum Mechanics

Why doesn't the electrical attraction between protons and electrons make the electron fall into the nucleus?

Quantum mechanics.

If the laws of physics consisted of only classical electromagnetic theory and Newton's laws of mechanics, then electrons going around a nucleus would gradually lose electromagnetic energy and spiral into the center and collide with the nucleus.

That doesn't happen and the theory of describes the law of nature that predicts a stable orbit is quantum mechanics. Quantum mechanics is correct and classical electromagnetic theory and Newtons laws have limited validity.

Quantum mechanics predicts discrete and stable electronic states as the ground state (lowest energy state) of electrons around atoms.


The electrons centrifugal force balances the electrical attraction (centripetal) force and thus does not fall into the nucleus.

The electron energy is the sum of the electrical scalar/potential energy -vh/r AND the vector energy cmV=cP. The vector energy is not recognized and is the so-called "Dark Energy" in Cosmology. The electron has matter and motion thus momentum, mV=P, this also gives the electron vector energy, cP. Physics has yet to recognize that Energy is a Quaternion quantity.

The Energy of the electron is W = -vh/r + cP = [-vh/r, cP]

and the Force is the first derivative of energy. Quaternion Physics also needs a Quaternion Derivative X =d/dr + DEL = [d/dr, DEL].

Force F is the first derivative of the energy W

F = XW = [d/dr,DEL][-vh/r,cP] = [vh/r2 -cDEL.P, cdP/dr -DEL vh/r + cDELxP]

F = [vp/r - cp/r cos(PR), -cp/r 1P + vp/r 1R + cp/r sin(PR) 1RxP]

The electron does not fall into the nucleus because the scalar force is zero. This is the Continuity condition: 0= vp/r - cp/r cos(PR) and

this gives vp/r=cp/r cos(PR) and v/c= cos(PR).

This is the case of the centripetal force vp/r is balanced by the centrifugal force cDEL.P, Divergence of the Vector energy, cP. The Divergence is the outward force and balances the centripetal , inward force. The cos(PR) is the angle needed to balance the two forces. At different velocities or orbits, the angle is different. The cos(PR) =v/c is the redshift of the electron and is the same cause of the redshift in Cosmology.

The speed of the electron is v=Z Alpha c, where Z is the Atomic Number and Alpha is the Fine Structure Constant.

The redshift cos(PR)= v/c= ZAlpha c/c=Z alpha and the limit is Z Alpha =1 so the Atomic Number is limited to Z<1/Alpha = 138.

Newton's Laws are correct when extended to Quaternion quantities. Newton's 3 laws are correct and anticipated Quaternions, specifically Newton's vector force anticipated the vector energy cP.

F=dP/dt = cdP/cdt = cdP/dr = dcP/dr the derivative of the vector energy cP !

The Quaternion nature of Physics is the revolutionary insight as to why the electron does not fall into the nucleus and why the earth does not fall into the sun!

this is absolute stupid,,,,the electron theriy is just a theriy, its not true....GE's tunelling microcope can see electrons, they are very small balls..

Quantum Mechanics

What is superposition theory?

The superposition theory is a theory in quantum mechanics that states that an object (that is microscopic or unaffected by coherence i.e. behaves in a way predicted by quantum mechanics) can be in more than one place at the same time. This arises partially from the uncertainty principle but also how waves behave. A easy way to imagine this is if you have too unopened boxes, one has an object in the other doesn't however you do not know which box has the object so in Quantum Mechanics this would be a superposition state - the object - because it is unmeasured is in both boxes at the same time. Now to describe how this superposition state "collapses" into the object being in only one box you have to describe or show the objects as waveforms - basically graphs describing the probability of finding the object in a certain position. In our box scenario the object will have two wave forms - as it is in a superposition state - one describing it as being in the left box and the other as the right but how these waveforms "collapse" into one is still up for debate the most famous being the Copenhagen Interpretation and the other the Many Worlds theory but that is for further reading.

Hope I helped!

Quantum Mechanics
Time Travel

What type of physicist studies time travel?

Theoretical physicist more than likely.

As far as time travel I fear physicists have already discovered what is worth to be know. Travel towards future is in principle possible. It is sufficient to move with a speed near the light speed with respect to the starting inertial reference (the earth for one of us).

The relativistic phenomenon of time compression provoke the time to pass much slower for the traveler with respect to the persons remaining in the "fixed" reference.

When the traveler returns in the initial reference (the earth in our example) he effectively traveled towards the future.

Unfortunately, travel towards the past is effectively impossible due to the causal nature of the laws of physics. As a matter of fact, reversing the time in only one phenomenon (the travel of our traveler in this case) violate the essential law of relativity that causal order has to survive between events happening in the same point of the space. Thus it is simply impossible.

(look, I'm not going to retype his entire response but: e-mc^2 thus a particle with a negative mass will go at a negative velocity and thus backwards in time. such particles are thought to be possible (at least not counted out yet) there are also a million other ways that intelligent forces can bypass naturally unbreakable laws such as wormhole's, however improbable they may be, given infinite time and flexible enough conditions anything is possible. so go ahead and become a theoretical physicist and prove this guy wrong.)

This renders traveling to future quite unattractive: It is impossible to return from such a travel.

Quantum Mechanics

Has Quantum Entanglement been proved or disproved yet?

Quantum entanglement was an observation in the 1930s, it's established as much of a fact as can be in physics since then. The current status is determining whether information transfer is instantaneous or has lag time.

Quantum Mechanics
Particle Physics

What is definition of electron clouds?

The composite quantum mechanical wave function describing the space of an atom in which there is probability of there being an electron at an arbitrary time and place.

Quantum Mechanics
Particle Physics

What is smaller than a boson?

Bosons are particles with integer spin which do not obey the Pauli Exclusion Principle, therefore a number of them may occupy the same quantum state.

In general, all bosons can be classified as either mesons (composite particles) or gauge bosons (elementary bosons). Pions are examples of mesons, while photons are examples of gauge bosons.

Since the name "boson" applies to a number of particles there can be no answer to this question.

Bosons are part of 3 families of fundamental particles described by the Standard Model of quantum physics, and being fundamental means they have no known substructure - i.e., there isn'tanything smaller than a boson. (The same applies to quarks and leptons.)

Quantum Mechanics

Is line spectrum obtained from filament of bulb?

filament of bulb

Quantum Mechanics

What is electron ballistics?

A ballistic electron travels a straight course through a semiconductor without scattering off any atoms. In other words it travels through a material as if the material had no atoms in it.

Quantum Mechanics

What is distance in the power formula?



P-power, W-work, t-time, F-force, d-distance

Quantum Mechanics

Was max ernst Jewish?

Max Ernst was born on April 2, 1891, in Bruhl, near Cologne, Germany,

the third of nine children of a middle-class Catholic family.

Quantum Mechanics

Who is the inventor of quantum theory?

Matthew Scazick

Max Plank

Quantum Mechanics
Units of Measure
Length and Distance

Define a light year?

A light-year is a unit of length equal to the distance that light travels through vacuum

in a year (about 5,787,499,810,000 miles). It is often confused as a unit of time.

The official definition of a light year uses the Julian year of 365.25 days and the speed of light 2.99792458 times 10 to the power 8 metres/sec, so a light year is 9.460730473 times 10 to the power 15 metres or 5,878,625,373,180 miles.

Salary and Pay Rates
Quantum Mechanics

How much do quantum mechanics make?

The inherent chaos is the field makes it impossible to pin down an exact salary.

Quantum Mechanics

What is K space in quantum mechanics?

K space refers to a space where things are in terms of momentum and frequency instead of position and time and the way you convert between real space and k-space (or Fourier space) is a mathematical transformation called the Fourier transform (and Inverse Fourier transform). This K-space also exists in classical physics. In quantum mechanics the space is made up of discrete values of K, whereas in classical physics K can take on a continuum of values.

Quantum Mechanics

Why do you normalise a wave function of a particle?

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

Elements and Compounds
Quantum Mechanics

Tiny particles in motion make up all matter?

All matter is made up of 'atoms', which are generally treated as tiny particles, although they have been shown to also have the properties of waves (just like light has both particle and wave nature). They are constantly in motion, and move faster in matter at a higher temperature. The temperature at which this motion is zero is -273C or 0K, absolute zero and is impossible to achieve.

Solid State Physics
Quantum Mechanics

What is Planck's quantum theory?

Max Planck assumed that the radiation energy is emitted in discrete packets called quanta rather than in a continuous way. The energy E of the quantum is related to the frequency ν by E = hν. The quantity h, now known as the Planck constant, is a universal constant with the approximate value of 6.626 X 10^-34 Js

Quantum Mechanics

What is the significance of quantum mechanics in chemistry?

The significance of QM in chemistry (quantum chemistry) is that it explains, in terms of electron energy levels, the behaviour of the different chemical elements at the quantum level, taking into account the wavelike properties of the electrons using Schrodinger equation to calculate those properties.

Quantum Mechanics

What is the fudamental assumption of quantum mechanics?

I'm not sure there is one, "The," fundamental assumption of quantum mechanics, but a basic assumption is that our Universe, at the sub-atomic level, operates at a probabilistic manner. In other words, we can no longer say, "This event will happen," we can only speak of the PROBABILITY that an event will happen.

I need to emphasize that QM assumes (and experimental evidence has shown) that it is NOT the case that we lack the instruments to determine anything more than probabilities, nor is it the case that QM particles "know" what will happen while we do not. It is that, in our Universe at the sub-atomic level, events are inherently probabilistic.

Nuclear Physics
Atoms and Atomic Structure
Quantum Mechanics

A quantum state with zero spin?

The theoretical Higgs boson would have zero spin.

The neutral and charged pions also have zero spin.

Two entangled particles, each with spin opposite to each other, would be a quantum state with zero net spin.

Atoms may also have zero spin, if they are in what is known as S-states (e.g. the ground state of hydrogen).

Quantum Mechanics

Why wave function complex?

because position of a particle in a wave (performing oscillations) is dependent on both time and the energy it is recieving.....

Quantum Mechanics

When did max planck discover quantum theory?

He published his work in 1900. It was VERY FAR from a full quantum theory, it was only an attempt to explain the spectrum of black body radiation with the idea that light came in chunks he called "quanta." And he himself did not think these quanta actually existed, he only noted this as a mathematical curiosity.


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