I read that lens makers used to use radioactive glass to increase the refractive index property of their lenses.

How radioactive are they?

Here are some example dosages; where would looking through the viewfinder for an hour fit?

http://xkcd.com/radiation/





Question: Would a meta-answer be a good idea?
Answer: I think this would be useful in the case of questions such as those discussed in What&#39;s the rationale behind closing a useful question with 70K views?, where a question has been locked and/or closed because there are a huge number of answers.  In many such cases, there are numerous duplicates or near-duplicates lurking in the undulating moebius strip of answer pages simply because people have eagerly added their contribution without taking the time to scan the 72 pre-existing answers to see if theirs is already there.

So allowing moderators to establish a single 'meta-answer' for such question would provide a way to merge duplicate and similar answers into one comprehensive (and comprehensible) whole.  The meta-answer would be "sticky", i.e. be presented first.  It might be necessary to only show it to those with a certain privilege level, or to visibly indicate it as a draft (or both) until such time as it's considered representative of the general body of answers to the question.

One problem I can see with this idea is that it would potentially involve a lot of tedious editing work.  The amount of work needed could be reduced / made remotely practical by providing a way to mark answers as having been incorporated into the meta-answer; such a flag would presumably be disabled or visibly expired if a compiled answer was edited.

I can't really think of anything that compilers could stand to gain from such work, since it would certainly have to be considered a CW-type undertaking.  Maybe a "maintainer" or "compiler" badge for people who do a lot of such edits?