Why is it OK to use electrostatics in Bohr’s Model if the electron is moving?

In the Bohr’s Atomic model, we have assumed the centripetal force to be provided by the electrostatic force between the proton and electron and derived the radius, energy of orbit and the velocity of the electron. However if the electron is not stationary, how have we used Coulomb’s Law for finding the electro ‘static’ force? … Read more

How to measure wavelength of gamma-rays

How can we experimentally measure the wavelength of gamma-rays, say for about 0.7MeV without knowing the exact energy and without measuring energy, i.e. sort of direct measurement. Answer The direct method is by crystal diffraction. Here is an article by Kessler et al (1988): High accuracy, absolute wavelength determination of capture gamma-ray energies for E≤5 … Read more

Why are neutrons present in an atom? [duplicate]

This question already has answers here: We know that the protons in a nucleus are positively charged. So why does the nucleus stay intact? [duplicate] (2 answers) Closed 7 years ago. I have a very stupid question perhaps, but please answer me. An atom consists of electrons, protons, neutrons. protons are positively charged and electrons … Read more

What is nuclide notation referring to? Only the nucleus or the whole atom?

sorry that this is an easy question but I am just a bit confused about nuclide notation. When you say e.g. 24094Pu, are you referring to the atom of Pu or only its nucleus? It doesn’t make this clear in my revision guide so I wanted to make sure. Answer Either. It’s context dependent. Chemists … Read more

Are all atomic collisions elastic? If this is the case, why?

In kinetic theory of gases it is considered all atomic collisions to be elastic. But if collisions are non-elastic the molecules must lose energy. Answer Are all atomic collisions elastic? If this is the case, why? No, this is one of the key approximations for an Ideal Gas. I will quote you the very first … Read more

What is the exponential (or geometric) rule (or law) for uranium enrichment?

Uranium ore starts at about .72% U-235… At ~20% U-235, it is considered to be about ‘90% of the way’ to weapons-grade uranium, which is about ~90% U-235… Because uranium enrichment in centrifuges follows a geometric (or exponential) law… I have read about this repeatedly when hearing about Iran’s enrichment program…. Does anybody know what … Read more

Is the artificial gauge field a gauge field?

The so-called artificial gauge fields are actually the Berry connection. They could be U(1) or SU(N) which depends on the level degeneracy. For simplicity, let’s focus on U(1) artificial gauge field, or artificial electromagnetic field. One can show that it is indeed gauge invariant. My criterion for a gauge field is that it should satisfy … Read more

What exactly is a hyperfine level as mentioned in the definition of a second?

I have a quite simple question: What exactly is a hyperfine level (or a hyperfine structure)? Maybe my question sounds (or is) stupid − I am not an expert in physics − but I didn’t find any description in the Internet which I understood. (Or more precisely: most of the descriptions said that it has … Read more

An electron in ss state

If an electron is in s state, for example in 1s state for Hydrogen or 5s state for Silver atom, ℓ=0. So,its total angular momentum L is also equal to 0. So, what is electron actually doing in s state. Is it actually not moving at all. I know that it has got spin, but … Read more