Wikipedia:Reference desk/Archives/Science/2022 August 23

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August 23

Measurement of the components of a radio wave

In Wikipedia ["Field strength meter" article] it is written that the intensity of a radio wave is measured with a field strength meter which is neither more nor less than a radio reception antenna with an electric current induced by the radio wave. But can we independently measure the 2 electrical and magnetic components of a radio wave? Malypaet (talk) 02:31, 23 August 2022 (UTC)

By Maxwell's equations, the two are linked. If you can measure the strength of one, you can compute the strength of the other. If I'm not mistaken, the relationship is given by $\|\mathbf {E} \|=c\|\mathbf {B} \|.$ Of course, they can be measured and the data obtained can then be used to test Maxwell's equations, or to compute the speed of light, or to calibrate the meters used for the measurements.  --Lambiam 08:57, 23 August 2022 (UTC)

In the far field (far from the source of the radio wave)), the electric field strength $\mathbf {E}$ (SI units V/m) and magnetic field strength $\mathbf {H}$ (A/m) are related by $\|\mathbf {E} \|=Z_{0}\|\mathbf {H} \|=c\|\mathbf {B} \|$ where $Z_{0}$ is the impedance of free space (about 377Ω). In the context of radio technology, the magnetic flux density $\mathbf {B} =\mu _{0}\mathbf {H}$ is rarely used.

In the near field (close to the source) there is no fixed relationship between $\mathbf {E}$ and $\mathbf {H}$ - it depends on the nature of the source. The $\mathbf {E}$ and $\mathbf {H}$ can be measured independently, using a short dipole and a search coil respectively - both need to be electrically small (small compared with the wavelength). catslash (talk) 23:50, 23 August 2022 (UTC)

When sailing a sailboat, in certain conditions you may find yourself in sync with the crest of a wave. So here imagine a point on the magnetic component very close to a charge in a receiving antenna. For an infinitely short time dt consider the origin of the frame at rest at this point in the magnetic field. On the principle of relativity, the charge is then in motion and the Lorentz force applies to it, with the antenna in the direction of this force we then find the Hall effect and finally a displacement of its charges synchronized with that of the transmitting antenna. The electric field component therefore only appears when charges meet, in a vacuum this component does not exist and the radio wave has only a magnetic component. As there is no measuring instrument not based on electric charges, nothing can invalidate this hypothesis, right? Malypaet (talk) 08:39, 24 August 2022 (UTC)

Term for not getting something

Is there a scientific or psychological word for the feeling of being upset or disappointed for not receiving something that should not be expected? An example from my experience: Our drink machine costs $1.50 for a drink. I put in $2 and I get two quarters back. Once, I got three quarters. After that, I was upset every time I used the machine because I only received two quarters. Then, when I realized my being upset was not justified, I noticed that this behavior is common. People expect things they should not receive and then get upset when they do not get it. In order to discuss it, I figure it is best ot use the proper word for it. 12.116.29.106 (talk) 18:44, 23 August 2022 (UTC)

If you agree to qualify the domain you are describing as, say, contextual conditioning, the situation is probably described but probably not named precisely. Or it is named (see Pavlov's Dog), but unfortunately not in accordance with the point-of-vue you are willing to use when commenting the situation: see Pavlov's Dog, again. There is a phenomenon of Combinatorial explosion arising once you are trying to mix several dimensions of point of vues and various dimensions of possible occurrences. Imagine that the drink machine is soon to be replaced with one automatically puncturing your bank account or credit card. You need a bug or foreign piracy to have your account credited instead of being punctured. However the resulting pattern will be different because it will not be an individual experience but simultaneously experience by numerous people. Consequently behaviors resulting from the event will be different. More probably several other disturbances from regularity are to be expected from the new usages made possible and imposed upon by the machine. All definitions preexisting the update of the machine have to be reinvented again: thus the fuzziness (and perceived inadequation) of the definitions: expectation confirmation theory --Askedonty (talk) 21:14, 23 August 2022 (UTC)

There's loss aversion, although I don't think it's about the moral aspect (I expected more, therefore I deserved more!) so much as a failure to think tactically, like the allegory of a monkey whose hand is stuck in a jar due to unwillingness to release the nuts within. Though the actual monkeys mentioned in the article seem much more sophisticated. Also I couldn't find a link for that allegory, it's not in Category:Metaphors referring to monkeys. Mentioned at Monkey pot.  Card Zero  (talk) 21:15, 23 August 2022 (UTC)

One way to describe it is being "spoiled". Another term is "entitlement". I'm also reminded of a Dilbert strip where the PHB is talking about what the customers want. Dilbert tells him, "The customers want better products, for free!" ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:48, 24 August 2022 (UTC)

• The closest for "I want my extra quarter" is probably the anchoring effect, whereby one is drawn to a certain particular reference point given previouly even if there is no rational reason to follow it. Now, I would not trust that all the studies mentioned on the page are correct (cough cough replication crisis) but the general effect certainly exists.

Here is an anecdote I kinda trust. In Deep Thinking, Garry Kasparov says he uses the following demonstration for his business consulting speeches. Audience members are given a written quiz with pairs of questions such as the following:

1. Is the height of the tallest tree in the world greater than X?
2. What is the height of the tallest tree in the world?

Rationally, the answer to question #2 should be independent of the value of X. However, different audience members have different values for X on their sheet, covering a ridiculous range (say, from X = 10 metres (33 ft) to X = 500 metres (1,600 ft)) and the answer to question #2 is well-correlated with X all across the range. (I kinda trust that example, because (1) if it can be used as a "stage trick" it should be fairly reproducible, (2) Kasparov’s account admits that it failed in one case - the questions are supposed to be stuff the audience does not know but can take a shot at answering; one of them was about Gandhi’s age at death, but one of the groups included Indian students who knew the exact answer, which broke the correlation badly.) Tigraan^{Click here for my talk page ("private" contact)} 09:16, 26 August 2022 (UTC)