Being able to turn invisible is always at the top of the “if you could have any superpower” lists. Just imagine what kind of mischief you could get up to if no one could see you. However, pure invisibility isn’t all it’s cracked up to be. Invisible Woman should be bumping into everything.
You see not the world, but its reflection. A friend’s face in the sun, the device you’re reading this on right now, everything you see is constructed from reflected and refracted photons that make it to your eyes. If no photons of light are bouncing off an object, it’s in the dark, it’s invisible.
So-called “invisibility cloaks” from Star Trek to Harry Potter aren’t breaking physics in theory, just using the necessity of photons to their advantage in practice. To be invisible, light has to either pass directly through an object or bend around it. Fictional cloaks most likely do the latter, as do our best attempts to recreate them.
But where all this cloaking gets it wrong, from Potter to Sue Storm, is the ability to see from inside the cloak. If light is bending around Harry or Storm, no photons will hit the backs of their eyes. No photons, no sight. If you’re the Invisible Woman, make sure you get a good look at where you’re going before you cloak.
Of course, there is a comic book explanation for Sue’s continued sight. She doesn’t passively become invisible — Invisible Woman actively controls where and how light is bent around her body. She makes sure that at least some of the bent light makes it to her eyes when cloaked. Sciencey enough for me.