Glass is transparent to visible light, but many types of glass are opaque to ultra-violet wavelengths.?

Question

what is meant by this?

Answer 1

This means simply that visible light passes through the glass, but ultraviolet light does not. Looking at the glass with your eyes, you can see it's transparent, right? Well if your eyes could ONLY see ultraviolet light, the glass would look pure black.

You can demonstrate a similar effect on your own with a camcorder. Turn the camcorder on and walk up to a TV or VCR or any appliance that has an infrared remote sensor. The sensors are usually covered by a black plastic panel--this plastic is opaque in visible light, but transparent to infrared. (Sort of the opposite as your ultraviolet question.) Point the camcorder at the black plastic panel and look through the viewfinder. Presto, you can see right through the panel! Why? Because camcorders (and digital cameras, for that matter) have the ability to see in the infrared spectrum as well as visible light, so the panel becomes transparent when viewed through a camcorder.

Answer 2

Ultraviolet light is basically just another color that humans can't see. It's like looking through a stained-glass window; the glass lets some colors through but not others, so all that reaches our eyes is what's transmitted by the glass. Most standard glasses let a wide range of colors through (in fact, most of the colors visible to the human eye) but don't pass the UV. That's why you can drive all day with the window up and not get a suntan, but if you roll the window down your arm gets burned.