How do the single photon energy and em-signal energy correlate? If the photon (as a quantum of the electromagnetic field) has no defined(?) amplitude, how does (or where from?) the electromagnetic wave's amplitude appear?  The formulation of the question is not quite precise, but the main idea is if we cannot define the single photon's amplitude, since $E=hf$ only (are there any other equations?), how can we talk about an amplitude of an EM wave, which is carried via photons (EM quanta)?
What is the relation between electromagnetic wave and photon? At the end of this nice video (), she says that  is a chain reaction of electric and magnetic fields creating each other so the chain of wave moves forward.  I wonder where the  is in this explanation. What is the relation between electromagnetic wave and photon?
Stop terminal auto executing when pasting a command Right, this is a slightly annoying feature because something this happens, and other times it doesn't, very odd.  I paste a command into the terminal with a view to tweaking its arguments, and sometimes it executes the second I paste it. Sometimes it doesn't.  This ranges from embarrassing ( posting nonsensical comments on an IRC ) to dangerous.   How can I shut this feature off for good? I never, never, never want the terminal to auto execute when I paste to it. How to set HttpResponse timeout for Android in Java I have created the following function for checking the connection status:  private void checkConnectionStatus() {     HttpClient httpClient = new DefaultHttpClient();      try {       String url = "http://xxx.xxx.xxx.xxx:8000/GaitLink/"                    + strSessionString + "/ConnectionStatus";       Log.d("phobos", "performing get " + url);       HttpGet method = new HttpGet(new URI(url));       HttpResponse response = httpClient.execute(method);        if (response != null) {         String result = getResponse(response.getEntity());         ...   When I shut down the server for testing the execution waits a long time at line  HttpResponse response = httpClient.execute(method);   Does anyone know how to set the timeout in order to avoid waiting too long?  Thanks! Any time I am inserting new point feature in QGIS, the Feature Attribute dialog box is popping up. Is there a way to prevent it? (I am willing to insert many points at once and this pop up box slows down the process). Interior product (contraction) symbol See the above excerpt from John Lee's Introduction to Smooth Manifolds. In differential topology and linear algebra, there's an operator called the interior product or contraction operator, denoted $\iota_X(\omega)$ or alternatively with some other "half box" like operator $X_|\omega$. Does anyone know how to markup that operator in LaTeX?   Google has turned up nothing except for this thread:   That thread did receive an accepted answer, which was \invneg from the MnSymbol package, but the suggestion given there does not seem correct to me. Or at least, it does not match what I'm familiar with. That answer results in an inverted negation symbol, whereas the contraction operator should have a stroke down at the floor of the line, and a long stroke going up almost the full height of the line. It can be found in many texts, but why can I not find the correct LaTeX markup? Annuity notation in LaTeX Recovering data from a faulty disk When I plug in a removable 1TB USB disk in my laptop, the operations led keeps blinking for a while and then you can hear the servo mechanism resetting with a short "tack".  I'd like to recover the data.    I believe there might be some way to get the data through low level IOs.    What I believe is that the mounting process assumes the disk is OK and I should prevent this before using ddrescue or something similar.  Does anybody have a solution to this problem? How to find effects of magical items? Similar to this , but specific to D&amp;D 5e, how are players meant to find out the effects of items/potions/scrolls/weapons/armor?  Say, they find a potion in some chemist's chest. It is red and smells nice. Should they perform an investigation/perception check? Or an arcana/nature check? If I tell the players specifically to do an Arcana check, then I am already hinting at the fact that this potion will have some magical effect. It could just be a natural elixir concocted by Druids to help your health regen.  Same goes for weapons. They find the legendary bow of X, which has a +3 to hit and a 10% chance of striking other enemies near the target. I describe the bow as unique, glowing, made from dragon scales and hovering on air. Would they investigate their properties? Or just I just let them fire at a wall until something happens?   Our playstyle so far has been to use active checks for a quick understanding of the item (drink a little bit of Potion as an Investigation check to find whether it heals or not, sensing magical properties of the bow with Arcana checks). When time is available, and experimentation is necessary, allow the PCs to do some creative testing and, based on their ideas, "After Y time, you realize that the bow sometimes hits several points of the wall instead of just your target".  According to the RAW, is there a specific way of checking the stats/effects of such items? Travelling in Schengen area while waiting for permit of stay renewal in Italy I have one feature-request with the objective of having duplicate questions with no answers:   To (try to) avoid people answering duplicate questions, add an alert that says the question has a probable duplicate if it has a close vote as Exact duplicate, asking the answerer to go to the original and answer there.   What do you think? My objective is letting the duplicate question exist for search purposes, but the answers centralized in the root question. How to avoid the wrinkle at the poles of the UV sphere? How to count number of words from String using shell How to add a new kernel to grub2 How can we add a kernel to grub2? i knew the stuff we could do with the former versions, but it seems to have changed. What files should we edit? Is there any way to increase the drop rate of items? How can I sanitize user input with PHP? Is $\{0\}$ a field? Consider the set $F$ consisting of the single element $I$.  Define addition and multiplication such that $I+I=I$ and $I \times I=I$ .  This ring satisfies the field axioms:   Closure under addition.  If $x, y \in F$, then $x = y = I$, so $x + y = I + I = I \in F$. Closure under multiplication.  $x \times y = I \times I = I \in F$ Existence of additive identity.  $\forall x \in F$ (i.e., for $x=I$), $x + I = x$, so $I$ is the additive identity. Existence of mulitiplicative identity. $\forall x \in F, x \times I = x$, so $I$ is the multiplicative identity. Additive inverse. $\forall x \in F, \exists y = I \in F: x + y = I$ Multiplicative inverse. $\forall x \in F, \exists y = I \in F: x \times y = I$.  However, because the additive identity need not have a multiplicative inverse, this is a vacuous truth. Commutativity of addition.  $\forall x, y \in F, x + y = I = y + x$ Commutativity of multiplication.  $\forall x, y \in F, x \times y = I = y \times x$ Associativity of addition.  $\forall x, y, z \in F$, $(x + y) + z = I + I = I$ and $x + (y + z) = I + I = I$, so $(x + y) + z = x + (y + z)$ Associativity of multiplication.  $\forall x, y, z \in F$, $(x \times y) \times z = I \times I = I$ and $x \times (y \times z) = I \times I = I$, so $(x \times y) \times z = x \times (y \times z)$ Distributivity of multiplication over addition. $I \times (I + I) = I$ and $I \times I + I \times I = I$, so $\forall x,y,z \in F, x(y+z) = xy+xz$   Based on the above, $\{I\}$ seems to qualify as a field.  If $I$ is assumed to be a real number, then the unique solution of $I + I = I$ and $I \times I = I$ is, of course, $I = 0$.  So, is {0} a field, or is there generally considered to be an additional field axiom which would exclude it?  Specifically, is it required for the multiplicative identity to be distinct from the additive identity? I want to load the new entries without reloading the page. I found a great solution for: The ajax script:  &lt;script&gt;     $(document).ready(function() {     var refreshId = setInterval(function()     {         $('#content').fadeOut("fast").load('http://neocsatblog.mblx.hu/new.php').fadeIn("fast");     }, 10000);      }); &lt;/script&gt;   And the php:  &lt;?php require_once("wp-blog-header.php"); ?&gt; &lt;div id="content" &lt;?php cyberchimps_filter_content_class(); ?&gt;&gt;          &lt;?php do_action( 'cyberchimps_before_content'); ?&gt;          &lt;?php if ( have_posts() ) : ?&gt;              &lt;?php while ( have_posts() ) : the_post(); ?&gt;                  &lt;?php get_template_part( 'content', get_post_format() ); ?&gt;              &lt;?php endwhile; ?&gt;          &lt;?php elseif ( current_user_can( 'edit_posts' ) ) : ?&gt;              &lt;?php get_template_part( 'no-results', 'index' ); ?&gt;          &lt;?php endif; ?&gt;          &lt;?php do_action( 'cyberchimps_after_content'); ?&gt;      &lt;/div&gt;   However, this is a special feature that works perfectly here:  However, the main page refuses to load new entries, I do not understand the reason for this, as we use everything the same. How do I implement basic "Long Polling"? Are there wizarding schools in the rest of the "magical" world? Are there other schools for witches and wizards in the rest of the world? In the books they only speak of 3 schools, but what about Asian or American people?  And even more, were they affected by the events happening in Europe? Rules and guidelines for drawing good schematics There are a lot of poorly drawn schematics here. A few times people have actually asked for critiques of their schematics. This question is intended as a single repository on schematic drawing rules and guidelines can point people to. The question is  What are the rules and guidelines for drawing good schematics?     Note: This is about schematics themselves, not about the circuits they represent. I've always managed my iPhone/iPad/iPod Manually, I recently updated to iTunes 11 and now I can see no way to get my music onto my device.  I used to be able to just drag songs from my library to my device, now there is seemingly no way to do this.  I can view the music on my device by clicking on it on the top right corner of iTunes, but I can't seem to get to a state where I can drag music from my computer onto my device.  I'm using iTunes 11.0.1.12 for Windows if that makes a difference.