Recent content by Ring

From “Fundamentals of Physics, Fifth edition, Volume 2” Halliday / Resnick / Walker It’s not only an electromagnetic wave but it is also a probability wave. That is, to every point in a light wave we can attach a numerical probability (the square of the amplitude of the electric field vector)...

By far the easiest QM text of them all is Michael Morrison's "Understanding Quantum Physics-- A Users Manual."

Oh and the reason the excited electron doesn't absorb the incident photon is because the incident photon's energy doesn't match the energy required to promote the electron to the next higher energy level.

As you guessed both stimulated emission and stimulated absorption occur. But the ratio of the emission transition rate to absorption transition rate is proportional to the number of electrons in the excited state versus the number of electrons in the relaxed state. This necessary population...

This is similar to the thought experiment, “what if the Earth were a cube"? All the water and atmosphere would be in an areas near the center of the faces and getting to the edges would feel like you were climbing a vertical cliff. Starting from the edges you’d have the longest steepest...

Mass and energy are not things they're properties of a system. If you define your system to include all the products of the interacting particles then the mass and energy remain the same. If a nuclear weapon is detonated in a vault the vault weighs the same before and after the detonation.

No, all I could find were qualitative discussions of the subject. But if you look at the relativistically correct equation for mass: m2 = E2 - p2 (c = 1) You can see that a system of anti-parallel beams has a net momentum of zero so m = E. On the other hand a system of parallel beams of...

Of course the above post only applies to parallel beams of light. Anti-parallel beams of light do attract gravitationally.

From sci.physics "No, the situation is more subtle than the options you have presented. What happens with two parallel beams of light is: their energy causes them to attract each other gravitationally. But their _momentum_ (which also gravitates, since it's part of their stress-energy)...

I agree that many texts, for the sake of simplicity, use this definition. But according to the most universally accepted definition of mass m2= E2 - p2this is patently untrue. What this entails is the redefinition of the system in the middle of the stream. If you're consistant in defining the...

Yes An individual photon has no mass, but a system of photons that has a center of momentum frame has mass equal to m = E. If the system momentum is zero before the interaction it must be zero after the interaction and therefore m = E - 0. Mass cannot be converted to energy.

Yes, but the mass of the system isn't the sum of masses of the photons, its m2 = E2 - p2. And in center of momentum frame p = 0 so m = E.

I don't understand what it is you're saying. Mass is a property of a system and in the center of momentum frame it's invariant--there's no conversion involved. Are you talking about the local mass deficit?

Nope. Fusion/fision isn't about converting mass to energy its about converting potential energy to kinetic and electromagnetic energy. In other words it's about changing one type of energy into another. The remnant of the nucleus has less internal energy and as a result of this decrease in...

Mass and energy are not the same thing. In special relativity there's a thing called the energy momentum four vector which in some respects is as basic as you can get. In any case, energy is the time component of the four vector, momentum is the space component and mass is the magnitude of...