Intangibility vs. Invisibility
Marvel has a comic character named Vision. This Avengers member has an ability Marvel has incorrectly labeled as intangibility. According to Dictionary.com, the definition of the word is: 1. Incapable of being perceived by the senses. 2. Incapable of being realized or defined. 3. Incorporeal. But Vision's power is density control. He can be hard as diamond or pass through matter. This got me thinking.
If light has mass, wouldn't light go right through an "intangible" person. That would effectively render them invisible and blind. Wouldn't it? I mean light wouldn't bounce off them to be reflected back to our eyes. And they would be blind because reflected light would pass right through their eyes.
One could go one step further and ask if they would still exist at this point. Unless they did have a way to become solid again, light wouldn't touch them. So would they exist anymore?