Energies Definition and 299 Threads

I'm reading a paper on photovoltaic hydrogen production and the author claims that for reasonable solar efficiencies the band gap must be less than 2.0eV. This I understand. My question is how will it effect the photon absorption if the band gap is much smaller. Say the band gap energy is...

Homework Statement If two bodies one light and other heavy have equal kinetic energies, which one has a greater momentum. Homework Equations The Attempt at a Solution the way i am solving this problem is , i am assigning any arbitrary values to both masses and velocity of anyone...

Homework Statement An atom of mass M is initially at rest in its ground state. A moving (nonrelativistic) electron of mass m_e collides with the atom. The atom+electron system can exist in an 'excited state' in which the electron is absorbed into the atom. The excited state has an extra...

Homework Statement I was going through my past question and answer, I then came across this: "The noble gases have the highest ionization energies in each period". I then wondered why and how the above statement is a reality. How can the above statement be true when the noble gases have...

Hi again! So, this time I have a ball with a mass m that I throw down from some point with a height h. I want to write the kinetic and potentiel energies that the ball has in the start and in the end for this ball that is falling to h=0. What I have thought of is that the ball must...

Hi, The Question i am trying to solve is " Calculate the magnetic energies of Cu and Al in an applied field of 5mT at 0K." As far as i can find is that Cu is not a superconductor and Al is a superconductor and has a critical field of 15mT, which is higher than the applied applied field so it...

I think I'm trying to reconcile quantum mechanics and special relativity . . . or whatever I'm doing I'm pretty confused. Ok, so the allowed energy states for a particle in a box are E_n = \frac{\hbar^2 \pi^2}{2 m L^2} n^2 . This seems to mean, as you increase the length L, the particle's...

Homework Statement We're modelling an ammonia maser with a double infinite square well defined by: V(x) = \begin{cases} V_{0} & |x| < b - \frac{a}{2}\\ 0 & b-\frac{a}{2} < |x| < b+\frac{a}{2}\\ \infty & |x| \geq b + \frac{a}{2} \end{cases} I have had no trouble with the assignment up until...

Homework Statement Place the following in order of decreasing magnitude of lattice energy. KF, MgS, RbI I'm not really sure how to do this without looking up the lattice energy values with each. And I don't think that is what our teacher wants us to do

So I'm working on a problem (Hartle problem 6, chapter 6) dealing with tachyons. So far, I have determined the four-velocity and the four-momentum (up to a sign) of a tachyon. I have, with the four-velocity being a unit spacelike four-vector, u^{\alpha}=\frac{\pm...

Hey everyone, So I've been a little bit confused about something, and I'd like some input on this: When I look at systems like the particle in a box, or the Hydrogen Atom, it's clear that the higher energy states of comparable shape have more nodes. This seems to always be true. For any...

Homework Statement Using a 1 electron model, evaluate the energies of the muonic K X rays in Fe assuming a point nucleus. Homework Equations The \Delta E is the difference between energy of the 1s state in an atom with a "point" nucleus and the 1s energy in an atom with uniformly charged...

The S-matrix can be written as the sum of the Feynman diagrams, divided by a factor of 1/sqrt[E] for each particle, where E is the particle's energy. Does this mean at large energies, the probability amplitude to scatter is unlikely? But how can such a statement be made when no physics is...

Homework Statement Calculate the difference in wavelength between the 2p→1s line in ordinary hydrogen and in deuterium (which has a nucleus containing a proton and a neutron).Homework Equations the difference in wavelength is related with the difference in frequences with the relationship ...

Homework Statement A Particle is place on a smooth sphere of radius b at a distance b/2 above the central plane. As the particle slides down the side of the sphere at what point will it leave? Homework Equations potential and kinetic energies The Attempt at a Solution no idea

Are particles that are not stable (for example top, bottom quarks; W and Z) when produced in particle colliders possibly stable at very high energies? Are third generation particles stable at high energies? Thanks, Mark

Hey guys I was just looking over a past homework problem and found something I'm not too sure on - A particle is in the ground state of a Harmonic potential V (x) = 0.5mω2x2 If you measured the energy, what are the possible results, and with what probabilities? Now I know the answer...

why carbon can form polymers and sillicon not? though both are tetra valent. explain this based on its orbital and bonding energies

Hello, i appreciate your help! Homework Statement In this website the drawing of the situation in the first exercise can be seen, for better understanding. http://wwwprof.uniandes.edu.co/~gtellez/fisica1/ejercicios-semana10.pdf The problem asks me to determine the minimum height h to allow...

Homework Statement Find the ratio of the translational kinetic energies of a ring, a coin, and a solid sphere at the bottom of an inclined plane. The bodies have been released from rest at the top. Assume pure rolling without any slipping. The Attempt at a Solution Well, I'm really not...

Is the CMK matrix a constant for all experimental energies that we can presently explore? Thanks for your help!

I hope this is a good place to ask this: I'm trying to model how an object such as a kevlar vest performs in stopping a high velocity projectile such as a bullet. I have only basic knowledge of energy and momentum etc. but can learn if directed. I can calculate the Ke of the bullet...

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Homework Statement Consider a three dimensional rectangular infinite potential well with sides of length L, 2L and 3L. What is the energy of the first excited state relative to the energy of the ground state? The second state? The third? The fourth? Homework Equations...

Hi. First post. I'm trying to understand if electronic energy levels have fixed values, or merely fixed expectation values (in the latter case, orbital electrons could have any energy and it's only the average that would be fixed). Here's my argument for the latter. If it's incorrect, could...

Hi! I'm wondering what the effects of a variable mass of elementary particles on the rotational and vibrational energy-transitions would be like? Would they increase, decrease or stay the same? Thank you for your help! Regards

Hi, I have been searching the net but couldn't find the dissociation energies of Cr2Cl3 & Cr2O3... Just knowing which is higher will suffice too & is there any other molecule with lower dissociation energy which could lead to Cr3+ ? Many thanks in advance.

Homework Statement An electron of know KE collides with a hydrogen atom in its ground state. With what possible KE may it rebound? KE = 11.5 eV 2. The attempt at a solution I assumed that the electron may either hit an orbiting electron and excite him (maximum layer is n = 2, change in KE...

A 69.2-kg skier encounters a dip in the snow's surface that has a circular cross section with radius of curvature of r = 13.2 m. If the skier's speed at point A in the figure below is 8.13 m/s, what is the normal force exerted by the snow on the skier at point B...

First of all, I would like to apologize if this question is in the wrong section of the forums. I'm not sure if the photoelectric effect should go into "Quantum Physics", "Classical Physics" or even "Homework & Coursework Questions" Descriptions of the photoelectric effect commonly states the...

Homework Statement (a) Calculate the disintegration energy when 232/92U decays by alpha emission into 228/90Th. Atomic masses of 232/92U and 228/90Th are 232.037156u and 228.028741u, respectively. (b) For the 232/92U decay in part (a), how much of the disintegration energy will be...

Homework Statement A satellite is to be launched from Earth to venus. It is to make two complete circuits of the earth, then travel to venus, and complete one orbit of venus in 12 hours. Find the velocities of the satellite around venus, around the earth, and the radius of the orbit around...

In post #549 here I answered: And then I was surprised by the comment of Tom, asking how the pairing was done. Well, I thought that I had discussed it in some thread in BSM, but after looking at it, it seems that I did only a few sparse remarks here and there. On other hand, people was not...

I'm having some trouble with the definition of binding energy and decay energy. Consulting a nuclide table (http://atom.kaeri.re.kr/ton/nuc5.html) I found out that 53Fe has a binding energy of 458380.194 +- 2.107 keV and decays to 53Mn by electron capture. The decay energy is 3.743 MeV and...

First off, I would like to apologize if I'm posting this in the wrong sub-forum. Anyways, I'm sorry if this is an ignorant question, but I am curious as to whether the 4 fundamental forces (electricity and magnetism, gravitation, strong, and weak) would theoretically continue to break down...

I wanted to know the average total energies of an isolated hydrogen atom's electron and proton separately. I came across a lot of equations I could try to use, but I figured I'd ask to see if this information has already been approximated. Thanks

Homework Statement The first ionization energy of an atom is the minimum energy needed to remove one electron. For helium, this is 24.6 eV. The second ionization energy is the additional energy required to remove a second electron. a) Calculate the second ionization energy of helium...

The common understanding is that below around 250Gev the weak force gauge bosons have mass and appear distinct from the electromagnetic force, with its massless photons. And that to explain this required hypothesizing the Higgs field, which acts like a superconducting field, in the vaccuum...

Hey all, am new here so please go easy on me. This regards observation of Markarian 501 with the MAGIC telescope. Gamma rays appear 4 minutes after the visible light. That high energy photons (gamma rays) travel more slowly through the "quantum foam" has been suggested, and even more mundane...

Howdy, Can anyone explain qualitatively (without using any maths) why a particle with a smaller mass has a greater probability of tunneling through a potential barrier than another particle with a larger mass but of the same total energy? Thanks

Homework Statement Suppose that a particle of mass m is confined to move in the x-y plane in a 2-dimensional box of length Lx = L and LY = ½ L. Calculate the energies of the six lowest states. Homework Equations not sure to set up this problem? The Attempt at a Solution the most...

If a diatomic molecule's vibrational energy is increased to the dissociation energy of that molecule, will that cause the molecule to rip itself apart? Is it the change in vibrational energy that causes the molecule to dissociate?

Homework Statement What multiple of the energy needed to escape from Earth gives the energy needed to escape from (a) the Moon and (b) Jupiter? Use the Table (link below) if necessary http://edugen.wiley.com/edugen/courses/crs1650/art/qb/qu/c13/fig13-19.gif Homework Equations...

I have a question which may seem stupid, but I think I missing something here. I see 2 equations describing allowed energies for electrons in hydrogenic atoms, being: E = -\frac{hcRZ^2}{n^2} And E = -\frac{RZ^2}{n^2} I assume that both are correct, but what makes the difference? Is it the...

Homework Statement A stationary uranium-238 nucleus undergoes alpha-decay. What is the ratio of the daughter nucleus to that of the alpha-particle? P.S. It's a practice problem for which I had the final answer, but I'm not sure how to reach it. Homework Equations I guess it's based on...

if i calculate the change in binding energy in a decay process such as B-decay using SEMF, and then i calculate the same difference in binding energy using the difference in atomic masses and electron masses. why are they different?

What is the highest possible energy per beam that the LHC can handle?

Homework Statement A meson (elementary particle) decays into two photons, each of energy 150MeV in its rest frame. Find the mesonic kinetic energy in the case of a symmetric decay in flight with an angle of 60degrees between the photon momenta (30 degrees for each particle on each side of the...

Question about internal energies... PLEASE HELP ME! What must be true for two objects of the same material to have the same internal energies? (Choose all that apply) a. The masses of both objects must be equal b. Both objects must have the same density c. The temperatures of both...

I am an A-level teacher so I don't want an answer in terms of anything too complicated (for my students!) The hydrogen atom has a ground state energy of -13.6eV. I am happy with this. This means that the electron needs 13.6eV of kinetic energy in order to become free of the nucleus...