The visualization tag has been applied to software related questions as well as questions involving light. Given that we already have a software tag, all software-related visualization questions are covered by that. The other two questions that use visualization for non-software reasons could work though I would personally like to see these two questions be tagged with something along the lines of light or electromagnetic-spectrum or electromagnetic-radiation.
In this case, I'd delete "visualization" for now. I would certainly use it in a software context, and the other two questions probably should use electromagnetic-radiation.
(Personally, I'd remove "visualization" from the invisible ink question.)
I just edited everything under visualization so there are no more questions there.
1$\begingroup$ Well that goal is only 2000 rep points away. That could be done in 10 days time. I'd bet your university and students will be quite understanding when you explain to them why you immediately need 10 days off :) $\endgroup$– PhilippSep 30, 2014 at 22:26
$\begingroup$ Oh no, I have access to the moderator tools now, but I haven't had a chance to figure out how to delete the tag. At the least, it's empty. $\endgroup$ Oct 1, 2014 at 2:15
$\begingroup$ Sorry, confused "moderator tools" with "trusted user" privileges. But have you read this post? Apparently, you have done exactly what is necessary to get rid of an unwanted tag by removing the tag from all questions. It already seems to have been removed from the system - at least it doesn't show up anymore under "tags". But if it comes up regularly it might be a good idea to declare it as a synonym for software. $\endgroup$– PhilippOct 1, 2014 at 11:15
$\begingroup$ I was just going editing some questions, and noticed that the electromagnetic-radiation tag was unused/undefined. Is there a reason for this? Simply searching "photon" brings up many questions that could fall under this tag. $\endgroup$ Dec 3, 2014 at 5:44
[tag:visualization]it renders and gives a link to the tag. Instant magic. $\endgroup$