New answers tagged

2

You can calculate an average power per square metre, but it's going to be a somewhat meaningless figure because the Sun only shines for part of the day and the strength of the sunlight varies continuously throughout the day. But if you want to go ahead this is how to do it. Suppose the total power (not just the PAR) per square metre is $P$ (in watts per ...


3

In addition to the quantum mechanical model of electrons being in bound energy states , in orbitals around an atom, the band theory for solids, a quantum mechanical model, is necessary to explain the interaction of metals with light. The electrons around an atom occupy more and more bound energy states. A photon that does not have the appropriate energy to ...


1

Intensity in this context often refers to only the number of alpha particles incident on a unit area per unit time. If you assume that the alpha particles only slow down and none of them are stopped completely, then the number passing through any area does not change with depth and the intensity in this sense is unchanged. Naturally the intensity in terms of ...


2

Actually, i would think you are rigth, too. Usually, such a Problem is described via the Bethe-Bloch Formula. If you do an alpha-particle experiment, you can even measure the attenuation of alpha-particles in air, for example. So maybe he meant something else and just put it queery?


0

Photon energy density does affect the expansion of the universe, similar to the effect of dark matter and dark energy. At the present time, however, the photon energy density has a much smaller effect than either dark energy or dark matter. This is due to the different ways in which the energy densities of the various components scale with the size of the ...


0

The first is, is my understanding described above correct? Basically, yes. The second is, how does this affect us healthwise? We are stuck with these debris of cesium-137 and strontium-90 for the next 30 or more years, but what effect do they have on us? Stochastic health effects (induced tumors, cancers, leukemia,…) of ionizing radiation are ...


0

No. A pair of neutrinos is pulled from the vacuum. One of them interacts with one of the quarks via the weak force, and they both change identity: the quark to another kind, thus changing the neucleon; the neutrino to an electron, which escapes. (The negative charge unit also moved from the quark to the lepton.) The electron escapes as the beta ...


2

As @dmckee pointed out in his comment, Radium is just at the "top of the decay chain". Specifically the decay chain looks like this source Now these decays all look like $\alpha$ and $\beta$ emissions - none of which could be detected from any distance (since both are massive charged particles, they lose a lot of energy over a short range). We need to ...


1

There is an intriguing possibility that the answer is yes, in a very fundamental way! All amino acids (except glycine) come in two chiralities, left-handed and right-handed, related by parity. However, all amino acids used in living beings are left-handed. Evidently, by chance, early in Earth's history, left-handed compounds gained an advantage somehow. ...


3

The core reaction would be $$ n + \nu \longrightarrow p + e^- \,,$$ which respects all the necessary conservation laws (it's diagram is, after all, a rotation of the usual beta decay diagram). I am not aware of a measurement of this particular process, but $$ {}^{37}\mathrm{Cl} + \nu \longrightarrow {}^{37}\mathrm{Ar} + e^- $$ (which obviously has the same ...


0

If you carry your example forward, then the total power emitted by a 1 m long copper wire that is carrying 1 A is just the sum of the power emitted by each electron. How many charge carriers are there in a 1 m copper wire with a resistance of 100 Ohm (since you had a field of 100 V/m)? Resistivity of copper is $1.7\cdot 10^{-8}~ \Omega\cdot m$, so a 1 meter ...


-1

According to microwave schematic it is 50 Hz 2000 Watt radiation. And metal shield don't protect good enough. It is danger to be near microwave.


0

The peak at 823.51 is two 411.78 keV photon being detected as a single photon. The odd peak structure is due to a "full" x-ray plus another partially scattered x-ray being as a sum peak.



Top 50 recent answers are included