# Tag Info

7

The radiation pattern of any dipole antenna looks similar to what you are showing in the 2D plots - but in your interpretation of the 3D pattern you have the axes wrong. A dipole antenna with the main axis vertical will transmit power in the horizontal plane, with less and less power as you go further away (inverse square law). If you measure the power as a ...

0

Ernest Moniz and John Kerry wrote an op-ed in the Washington Post about the recent nuclear deal with Iran. In it, they say that even though inspections can be delayed for 24 days, that delay is not a problem .My question is: how does this detection work, and how hard is it to defeat? Let us have the info as to how the monitoring of Nuclear establishments/...

-1

To expand on the above answer by @PhysLab (which is very well written), the answer depends on how "in depth" you want to look at it. Before discussing energy transfer, let's cover a few fundamentals, because these are slippery concepts and often misunderstood. (Including by me, so fingers crossed!) Let's look at what "energy" and its "transmission" involves....

2

Energy transfer can be thought to occur via the exchange of a 'virtual particle'. In nature, there are 4 fundamental forces, namely: 1. Electromagnetic force 2. Gravitational force 3. Strong force 4. Weak force Each of these forces have a different exchange particle: For instance, the exchange particle for EM is a photon whereas that for the strong force ...

2

The question uses the term "Usually" which is not a correct description , however the decay schemes can be understood by analzing the process in detail. An alpha particle is identical to a helium nucleus, being made up of two protons and two neutrons bound together. There are models in which a nucleus can be seen as cluster of alpha-particles; say Carbon -...

1

Since the comparison is to air molecules I assume this is a question regarding very small conductors. The premise of the question is incorrect. This can be seen qualitatively by observing that the reason Rayleigh scattering by a dielectric particles occurs is that they reduce the electric field impressed on the particle. For a perfect conductor, the electric ...

1

Photon number density The number density of photons in the Universe is roughly 450 per cm$^3$ (a tad larger than the approximation in the source given in the comments, which uses the average photon energy), and is dominated by the Cosmic Microwave Background (CMB) radiation. Photons from stars/galaxies are 2.5 to 4.5 orders of magnitudes smaller in number, ...

0

In condition one it would not impart a side vector, but it would impart a side vector in condition two. Think of it as the direction the craft is "pushed" is halfway between where the light is coming from and where it ends up. If the light comes from the sun, 0', and is reflected directly back toward the sun, 360', the difference is 180' and the craft is ...

0

You can try Modern Problems in Classical Electrodynamics by Charles Brau. I think it is relatively clear in this book. At least I hope you can find the end-results in Zangwill or Brau. Then you should after trying be able to get there yourself. Start from the expression for the electric potential. In the integral there is a $\frac{1}{|\bar{r}-\bar{r}'|}$....

1

Absorbed dose for a given tissue or body organ can not be easily calculated using simple equations, even though it is simply defined as "amount of mean energy imparted per unit mass" , because it depends on so many other factors. Absorbed dose for a given material can be measured using devices called as Dosimeters such as (Calorimeters, ion-chambers, or ...

6

Electron capture Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shell. This process thereby changes a nuclear proton to a neutron and simultaneously causes the emission ...

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The decay of potassium-40 to argon-40 is either a $\beta^+$ decay in which what is emitted is not an electron but a positron $${}^{40}{\rm K} \to {}^{40}{\rm Ar} + e^+ + \nu_e$$ or, more frequently (if we have whole atoms), an electron capture that you mentioned in which no charged leptons are emitted at the end! About 11% of the potassium-10 decays ...

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