In my mind, it depends on how you became invisible. As there are numerous ways of accomplishing this, I think each should be taken separately:Option the First
: You are invisible because all light passes through you.
If this is the case, then ultraviolet radiation would be irrelevant. It, like all other parts of the electromagnetic spectrum, would pass straight through you. If this is the case, you are also likely to have the power of walking through solid matter. Good for you!Option the Second
: You are invisible because the visible portion of the electromagnetic spectrum passes through you.
If this is the case, then the UVA and UVB rays that cause sunburn would still affect you. You had better hope that you're one of the people that can turn clothes invisible with them, or you're in for some nasty burns in nasty places!Option the Third
: You are inside a wormhole
If this is the case, then all light is being bent, which makes it less likely that it will come into direct contact with your skin. Also, you might be dead. We don't really know yet.Option the Fourth
: You are covered in metamaterials
If this is the case, light is being bent around you without being absorbed or reflected off of you. UV would not apply, thus, no sunburn. Besides, you're completely covered anyway, so no need to worry about getting burned.Option the Fifth
: You are under an invisibility cloak (sorry Niffler, I beat you to it)
Again, totally covered up. No worries about getting burned. Besides, magic usually comes with automatic SPF 30. It's one of the benefits that is often forgotten. That's why Harry, Ron, and Hermione are all so pale!
So remember, unless light isn't touching you, it's still best to wear a good sunscreen when invisible.
ESPECIALLY if you can't make clothes invisible too.