I think it is a good reason cause if the water was bad or not what it claims then 100%of the people would be complaining about it
The answer is electron microscope, the magnification can be so high that it can be very expensive, most schools doesnt have them, mostly found in universities or some laboratories. the ones we usually use in home or schools are light microscope
To protect our eyes from moisture and light. Example: from sweat. It can also reduce the amount of light that gets in your eyes and keep dirt away from them too.