Frequently Asked Questions (FAQ) for Led Mirrors

1. Smallest Packets of Electromagnetic Wave - Confused

It is not possible to do. As it turns out, there is a fundamental linkage between the frequency of electromagnetic radiation and the smallest amount of energy that can be emitted or detected at that frequency. This was first determined by experiments, and analysis of the results led to the theory (theories) of quantum mechanics. Key experiments included measurements of the spectrum of black body radiation (see Black Body), and measurements of the energy and number of electrons emitted when light of various frequencies and intensities illuminates a metal surface (see Photoelectric Effect). All that said, it is still possible to manipulate photons to change their energy. For example, a photon that reflects from a moving mirror can gain or lose frequency (and energy); but the relationship between the final energy and frequency will always be $E hnu$. ($E$ is the energy in the photon; $h$ is Planck's constant, and $nu$ is the frequency of the photon)


2. How do we determine molecule chirality in these examples?

Although you have arrived at the correct answers and seem to have followed a reasonable process for getting there, it's important to be precise with the use of terms like symmetry and chirality. For a molecule to be chiral, it must be non-superposable with its mirror image. It's important to really embed this definition before talking about symmetry and things like chiral centres. For example, it is possible for molecules to be chiral without any chiral centres, and it's possible for molecules with multiple chiral centres to be achiral.Now, symmetry is a different, but related, topic. A molecule with a point or plane of symmetry will be achiral. However, molecules with a rotational axis of symmetry can still be chiral, eg. many often-used chiral ligands are C2 symmetric.So, in answer to your question, "What am I missing? - I would just say: the rigor in use of the terminology. Your approach of drawing different conformers of the molecules with two chiral centres and looking for a plane of symmetry (that shows the molecule is a meso compound, and therefore achiral) is sound and led you to the correct answers


3. Why does video rendering begin at the top left corner of the screen?

Probably because TV and CRTs scanned from the top left. Video cards store the screen buffer in this order, too, so scan-out from the screen buffer in left-to-right, top-to-bottom reads sequentially increasing memory addresses. Addressing video RAM as a 2-dimensional arrayextern int32_t screenbuf480640;

screenbuf00 RED;would modify the top-left pixel. My theory is that this led to graphics APIs using coordinate systems with 0,0 at the top left, even device-independent APIs (not 640x480 or whatever), because that choice mirrors direct addressing of video RAM. (and saves one subtraction every time a Y coordinate has to get mapped to a memory address.)As some comment point out, not ALL graphical coordinate systems have the origin at the top left, but it is extremely common for graphics APIs as well as UIs, and for example window coordinates in the X Window System.


4. NOT gate with PNP transistor

It's the mirror image of the NPN solution: emitter to Vcc instead of ground, load resistor between collector and ground instead of between collector and Vcc. edit

Like JustJeff says, make sure your input high voltage is high enough. If it is less than Vcc - 0.6V the transistor will be always on, or at least conduct partially, which shows when your LED isn't completely off. You can make the base voltage higher by adding a resistor from base to Vcc. Together with the base resistor it will form a divider. Example: say Vcc 5V and your input high voltage is 4.2V. That's too low, the transistor will always be off. If you place a resistor between base and Vcc the same value as your input resistor, the base will be at 4.6V and the transistor will be off.


5. Did George Washington say no political parties?

I went to add some notable references to the question and was led straight to the answer.In Washington's Farewell Address, 1796, he warned of obstructions that:put, in the place of the delegated will of the nation the will of a party, often a small but artful and enterprising minority of the community; and, according to the alternate triumphs of different parties, to make the public administration the mirror of the ill-concerted and incongruous projects of faction, rather than the organ of consistent and wholesome plans digested by common counsels and modified by mutual interests....Let me now take a more comprehensive view, and warn you in the most solemn manner against the baneful effects of the spirit of party generally.

This isn't just my quick interpretation. In an opinion piece, Robert Alexander wrote for CNN:In his farewell address, George Washington warned of the "continual mischiefs of the spirit of party" making it the "interest and duty of a wise people to discourage and restrain it." In other words, he cautioned against the dangers of political parties.Read the whole speech for more.p.s. Democracy wasn't an American invention and it wasn't young in Washington's day. Even American democracy wasn't young by 1796


6. Flyback smps or floating buck converter?

You may want to consider a AC-DC converter off-the-shelf. The reason why is that 220 VAC converted to DC is 311 VDC, quite a shock hazard. Switching power supplies need expert design engineering. We have helped many with LED supplies, but not at such a high voltage (180 VDC). Most DIY stuff for LED's is limited to 100 volts.Yes, that first link (MP4001) would be a good choice. The limit would be the voltage and max current of the MOSFET that drives the LED's, which can be any color by the way. Just remember that this is NOT isolated from the main AC supply so even touching an LED could be a shock hazard.The second link (AL9910_A) seems like a mirror image of the first, but it has a much more complete datasheet with warnings for this-and-that. Buy a 500 volt MOSFET rated no more than 5 amps. The reason is that 'beefy' MOSFET's tend to need a lot of drive current, which these tiny IC's cannot do


7. How does Mathematica use system environment variables?

The Mathematica variables you mention are unrelated to any system environment variables. It is not correct to think that they mirror any system environment variables. The similar names (as well as the use of $ in Mathematica) are just accidental.

In particular, $Path has nothing to do with the system's PATH environment variable and serves an entirely different function. I thought this important to point out because people have confused these in the past which led to all kinds of trouble.While it is true that Mathematica will be affected by certain environment variables, such as MATHEMATICA_USERBASE, there is no general correspondence between any $-variables in Mathematica and environment variables.

Regarding the use of $ in Mathematica: it is the only non-alphanumeric character that is allowed in identifier names. It is customary to name global constants as $... in Mathematica code, similarly to how it is customary to use lower-case names for non-public or user-defined symbols. This is just a convention, it does not indicate any relationship to environment variables


8. How many times has Dumbledore outright lied to Harry (or anyone)?

Dumbledore lied to Minister Fudge in OoPFrom OoP, chapter 28'Dumbledore's Army, Cornelius,' said Dumbledore, still smiling as he waved the list of names before Fudge's face. 'Not Potter's Army. Dumbledore's Army.''But - but -' Understanding blazed suddenly in Fudges face. He took a horrified step backwards, yelped, and jumped out of the fire again. 'You?' he whispered, stamping again on his smouldering cloak.'That's right,' said Dumbledore pleasantly.'You organised this?' 'I did,' said Dumbledore.'You recruited these students for - for your army?'Tonight was supposed to be the first meeting,' said Dumbledore, nodding. 'Merely to see whether they would be interested in joining me. I see now that it was a mistake to invite Miss Edgecombe, of course.' Marietta nodded. Fudge looked from her to Dumbledore, his chest swelling.'Then you have been plotting against me!' he yelled.'That's right,' said Dumbledore cheerfully.


9. Was the decrypting of communications in WW2 a one-sided effort, or did Germany also do it? closed

The Germans certainly tried, and did have some successes, but not on the same scale as the Western Allies. They read British naval ciphers until 1943, which contributed to their successes in the Battle of the Atlantic, and were able to eavesdrop on the scrambled telephone link between the UK and USA. Their lesser scale of success seems to have been due to the fragmentation and duplication of their efforts. A single large-scale organisation like the British Government Code and Cypher School (GC&CS), based at Bletchley Park, was quite foreign to Nazi ideas of organisation. They also suffered from "mirror-imaging", assuming that their enemies worked in the same way as them. They found it hard to believe that anyone could assemble the scale of effort required to break their ciphers, which led them to discount the clues that the Enigma was broken.


10. Controlling an LED using a transistor (TL188)

It really doesn't matter if you use a PNP or NPN transistor, they are just mirrors of one another. If you have some common anode displays then just start directly with the PNP's.The flaw I see in your circuit is that you should always use 2 resistors to drive a LED (See schematic). R2 (as you already have) will limit the current to the LED; 220 Ohm you as illustrated is fine.R1 is needed between the I/O pin and your transistor. This will limit the current through the I/O pin. For what you are attempting a resistor in the range 1K to 2K should do, even if you're switching a few LED's in parallel.

If you provide complete details of your setup we can always refine the calculations. One can then take into account the total currents from your displays, the amplification factor of the transistor (hfe) etc.


11. Final scene in Planet of the Apes (2001)

It's been a few years since I've seen that movie but the actual DVD cover had an insert that showed a time map to help make sense of the movie. It is two different planets as it was in the original novel Monkey Planet and Mark Walhberg does end up back on Earth (not a duplicate Earth) in the current time. Apparently the time vortex works in reverse so that the first one in is the last one out. The space ship Oberon goes in last but has crashed thousands of years in the past. It was originally planned to have at least a sequel which would have explained the current Earth better. The ending of Burton's film confused just about everyone, so much so that when the DVD was released it included a chart explaining how the apes on the planet were able to build their own space ship, enter the vortex, end up in Earth's past, and end up dominating that planet as well. The problem here, without the chart the ending makes no sense.


12. Did Brock Chisolm, the first director of the United Nations WHO, say this anti-individualism quote about a world government?

Researching this quote has led me down the predictable spiral of conspiracy theory bloggers. They generally don't cite their sources, and when they do their sources are either just more conspiracy theorists or complete fabrications.This conspiracy theorist blogger sources the quote to the 1946 issue of Psychiatry. That issue is mirrored here, in a format that is text searchable. I searched for the whole quote, the word "achieve", the phrase "world government," and "traditions." None of those searches found the quote. I do not believe that the text contains your quote.

(I must tip my hat to this metabunk thread who found this source, and @Nat and @JohnDee who helped find it.)The book, America in Prophecy repeats a longer version of the quote. His source is, "as quoted by Dr. J. R. Church, "The New World Order," Prophecy in the News vol 24 no 4 April 2004, 28.

" The date, title, and author match this conspiracy theory article. The article does not mention Chisholm at all, but has a similar uncited quote:Author Ralph Epperson commented: In Addition to destroying mans basic loyalties to family, nation and religion, the nation must be conditioned to the belief that less is better than more.

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