Does Light (EM Signal) undergo accelration during reflection? Since Average acceleration is defined as, Average acceleration over a period of time is the change in Velocity divided by the Duration of the Period.  Does Light (EM Wave) undergo acceleration during reflection from mirror or any other surface?
What happens when a photon hits a mirror? When a photon of light hits a mirror does the exact same photon of light bounce back or is it absorbed then one with the same properties emitted? If the same one is bounced back does it's velocity take all values on $[-c,c]$ or does it just jump from $c$ to $-c$ when it hits the mirror?  Or, is the phenomenon of a mirror better explained using a wave analogy? If so, what is this explanation?
Using 'for' as a coordinating conjunction at the beginning of a sentence – is this acceptable? As I understand it, 'for' is a coordinating conjunction. Learning German as a second language has taught me specifics about reforming sentences, but it is an awful lot less common in English. If I were to rearrange the sentence: "I ate lunch, for I was hungry," so that 'for' was the first word of the sentence, by my reckoning I should end up with "For that I was hungry, I ate lunch." Does this new sentence have any grammatical errors? I inserted the word 'that' after 'for', because without it the sentence didn't sound right. Should I have? Is there a rule for that? Thank you in advance, an aspiring author.  Additional Information:  I am not having problems with the sentence, this is a general question to increase my knowledge of the manipulations of coordinating conjuntions. Prove by contradiction (not using a calculator) that $\sqrt6 + \sqrt2 < \sqrt{15}$? How to use an alpha map in Blender Render? How does linear regression use the normal distribution? I have two questions for you guys. I really appreciate your help.  1.- Is there a way to rename an Availability Group?  2.- Is there a way to get the T-SQL statements in order to re create a Availability Group in case that I need to drop it and create it again?  If there's information that you want me to share, please let me know and I will provide it. Ubuntu 19.10 change desktop environment I've installed another desktop environment which I would like to try. I am not sure how to switch to it.  Is there still a button on the log in screen that will switch desktop environments? This same question for previous versions of ubuntu yields screenshots of this button. But I cannot find any button on the log in screen that does this.  So, in ubuntu 19.10, does there exist a button to switch desktop environments? If so, where is it? If not, what is an alternative method to switch desktop environments after I've already installed one?  ██████@████-linux:~$ ls /usr/share/xsessions gnome-flashback-compiz.desktop    ubuntu.desktop gnome-flashback-metacity.desktop   The gear icon does not show up for me, as the answers indicate it should.    Solved. I was not logged out properly. I locked the screen thinking that was logging out. Logging out properly fixed the issue. Can we get by as English speakers visiting Iceland? We're going to Iceland for the first time in September. Will we be able to get around ok just speaking English, or should we try to learn some rudimentary Icelandic? And is that even what their language is called? Nested Virtualization What I do: I want to write a kernel module that does stuff to the KVM data structures. But I don't want to run it on the real machine, so I run one guest, inside it I run another two guests, and want to test my module.  The problem: VirtualBox (which now runs the outer guest), doesn't support nested virtualization, and when I cat /proc/cpuinfo | grep vmx I get no output.  What can I use that has nested virtualization?  You may look at my  to get an idea of what I want to do. Internet through wireless hotspot, intranet through wired network - can I use both at the same time? I have been tring this for a while now, without success. I have read online this can be done, either by changing the default gateway (DG) or messing with the DG's metric  The short story is: I need to connect to my company's ERP system (port 80 for some web services and port 22 for sftp and bash) with using my notebook computer's LAN card - but I can't connect to the Internet on this network. So I have my mobile phone's 3g hotspot when I need to go online. But I want to use both at the same time without so much as opening another web browser process.  At the moment, I am using the ERP system regularly - and whenever I need to go online to check a mail or research something related to work, I need to unplug the network cable so the wifi can kick in... which is starting to become annoying especially if I am connected to the ERP system using FTP (Filezilla) or Shell (putty)  Can someone help me with the configurations?  Below are some of the details I can provide:  Wired network - office LAN - for connection to the ERP system: DHCP -    Yes IPv4      10.64.200.245 Subnet    255.255.240.0 DG        10.64.193.254 DHCP Serv 10.64.17.191 DNS       10.68.72.200           10.68.20.200 WINS      10.68.77.200           10.64.20.200   Below are the details for my WiFi internet connection - over my mobile hotspot  DHCP      Yes IPv4      192.168.43.39 &lt;- I'm guessing this changes every time I restart the wifi subnet    255.255.255.0 DG        192.168.43.1 DHCP      192.168.43.1 DNS       192.168.43.1   Finally, here is the tracert results (btw, I'm on Windows 7, 64bit and the remote system should be on Linux) - the target ERP ip address is 10.76.142.39  Tracing route to 10.76.142.39 over a maximum of ...    1    &lt;1 ms    &lt;1 ms    &lt;1 ms  10.64.193.253   2    &lt;1 ms    &lt;1 ms    &lt;1 ms  10.64.4.13   3    &lt;1 ms    &lt;1 ms    &lt;1 ms  10.76.23.124   4     1 ms    &lt;1 ms    &lt;1 ms  10.76.23.93   5     1 ms    &lt;1 ms    &lt;1 ms  2xx-xx-xx-9.adsl...   6     1 ms     1 ms     1 ms  2xx-xx-xx-9.adsl...   7     1 ms     1 ms     1 ms  2xx-xx-xx-10.adsl..   8     2 ms     1 ms     2 ms  10.76.135.125   9     1 ms     1 ms     1 ms  10.76.142.39   sorry, I had to mask out some details above... wasn't sure if they would have any confidentiality issues.  Any help is much appreciated. What's the difference between a shunt resistor and a four-terminal resistor? I want to know if the four-terminal resistor and the shunt resistor are the same.   Is there another use for the four-terminal resistor except measuring current? Closed unit interval is connected proof Let's say that a player uses the ready action and says "If a character aims at me with a weapon, I'll use Teleport to move behind cover."  What happens? Does this work? If not, please cite the rules to explain why not. I just picked up a copy of Windows 7 Pro OEM for install on my computer.  Guy at the store said the only real difference between OEM and standard retail box was tech support.  However, the outside of the box has this big warning that says "The software must be installed with an OPK"?  What is the OPK?  Is it really necessary?  The MS site about it seemed to say it was optional.  EDIT:  BTW - I'm just an individual tinkerer, and not a System Builder Company Employee.  I should have made that clear.  I've used sysprep in a professional setting in the past, so I'm somewhat familiar with its concepts. Confused about complex numbers I am confused about something: \begin{eqnarray}     (e^{2 i \pi})^{0.5} = (e^{2 i \pi \cdot 0.5})= e^{i \pi}=-1 \end{eqnarray} but \begin{eqnarray}      e^{2 i \pi}=1~ and~ 1^{0.5}=1  \end{eqnarray} where is my mistake??  thanks I'm unable to access the following website from my Internet Explorer 8 under Windows XP with Internet Explorer unable to display web page error. By the other hand the FireFox browser at the same Windows XP can access this website.  How to solve the issue with IE8 ? How can I make a single event handler handle ALL Button.Click events? I have watched the series of Two and a Half Men two times now till the latest episode, but can't understand why either Charlie or Walden just don't kick Alan out? I mean it is a bit cruel but they are shown to put up with him even though he gets up on their nerves (even got on my nerves).    Some examples off the top of my head:   He became the reason of his first engagement with Mia to be broken up.   He once set up his curtains on fire after ruining his day.   He invited his girlfriend/assistant to move in without his permission and started acting like he owned part of the house when he didn't even pay rent. He acted sickly and dying (Walden's time) and tricked him out of money for his care and comfort.   He deliberately tried to break his relations (Walden's) just so he can keep sponging off.   I know not the best examples, but if not in every episode then in every alternate episode he is shown to getting up on their nerves and they just keep on telling him to leave. Why don't they just kick him out? Why put up with such a leach? I'm trying to remember the name of a series of books about a boy who works with dragons.  Dragon's blood (or maybe it was slobber?) is acidic, and the children who wrangle these dragons often end up with deep pock marks.  On this world, days are like ours but nights get very cold, requiring anyone stuck outside to find a shelter until dawn (not the false dawn)  The other thing I remember is that in one of the books by slicing open a dragon and spending the night, the character emerged with special dragon powers. Enabling GPU rendering for Cycles? I hear so many terms involving the word "linear". Linear function, linear equation, linear system, linear operator, linear transformation, linear mapping, linear space, linear algebra, linear electrical circuits, linear filters, linear electrical elements, linear approximation, linear optimization.  I'm getting crazy trying to understand the application of the "linear concept" to all this aspects (function, equation, mapping, system, operator, transformation, algebra, etc.) and I wish to know the one essence that is to be linear. What something has to be to be linear? If I say something is linear, what do I know for sure about that something (no matter what the something is)?       I heard a definition of linearity is by homogeinity (scaling the input results in a scaled output) and addition (summing the inputs results in summing the outputs). Can I apply this simple definition to all the branches (operator, mapping, system, transformation, algebra, ...) I mentioned ? Do they all behave like a line ?  y = ax + b, for example, is a line but doesn't behave like a line because y is not linear.