How useful is glass?

Answer 1

Glass is useful for the formation of lenses (used to magnify or demagnify light) and it is also useful for containing something without blocking light passage into/out of that container. Ie: A wind shield on a car blocks the interior of the car from the outside world (or at least it does for the most part) but light still passes through it, so the driver can see out of the car, and avoid colliding with something that could cause damage to the car, other people, other cars, or something else.

Answer 2

Reasons for glass include its use for windows to provide a means to view through a barrier for protection. Mirrors to reflect or refract light and allow us to see behind us. Eye glasses to correct our vision. Dishes for eating on and glasses to drink from. Fiber optic cable to send information at fast speeds. Lens to angle light so we can see far objects in telescopes or for magnifying objects up close.