You have to move around so that you can see the WHOLE fluorescent question mark before you can solve it. You have to find the whole thing, then properly align the whole thing (by moving both Batman and/or the camera), and then scan.
 
Usually the "period" part of the question mark is located somewhere else from the "squiggly" part of the question mark, but not always. 
 
These things, by the way, can be a TOTAL bitch to line up sometimes. Once you've found it all, just keep trying and trying until the scan works. Sometimes it's just a micron adjustment to make it work. And other times, you're just totally in the wrong spot and you have to find an entirely new viewpoint.
 

you gotta line it up so the camera sees a full question mark and then scan it

" Usually the "period" part of the question mark ..."

That's my only real complaint about the game is it is so bloody picky over how things are aligned. I get it with the question mark riddles because you need the period at the bottom of the question mark to have a complete one, so having it aligned makes sense. Some of the regular riddle puzzles though are just too particular about how they should be lined up. I remember the firefly one and i was trying to get that stupid newspaper article lined up just right for about 2 minutes before the game accepted it. 
 
If I'm close enough to it and looking at it, it should accept it straight away.
 
Only complaint about the game, but it is a phenomenal game

" @emkeighcameron said:

" Usually the "period" part of the question mark ..."

you said period.    And, i played through the whole game without solving any question mark riddles.. i remember seeing them in the GS video review.. arent i a big chump "

" @Ahmad_Metallic said:

" @emkeighcameron said:

" Usually the "period" part of the question mark ..."

you said period.    And, i played through the whole game without solving any question mark riddles.. i remember seeing them in the GS video review.. arent i a big chump "

lolz  and I got them ALL the first time through, so I'm way cool "