I was told that uv rays can not go thru glass but can go thru quartz. Is that true?
Asked by: Steve
You are correct; quartz is a good transmitter of UV rays. Most glasses are opaque to UV.
UV rays are electromagnetic waves (EMW) that have wavelengths which are smaller than those of visible light. Wavelength is measured in units of length (which is meter). Since the wavelengths of EM waves are usually very small, fractions of a meter are used - most commonly nm(nanometer) or A(Angstrom). Note that 1 nm = 10-9 meters (or one millionth of a milimeter), 1 A = 10-10 meters.
The UV range is from 0.1 nm to about 400 nm (or from 100 A to about 4000 A).
The visible light wavelengths are longer, between 400 nm and 700 nm.
Quartz will transmit UV from 180 nm to 400 nm. Since quartz is made of silicon dioxide, glasses made from a high proportion of this material will also readily transmit UV. One such glass is known as VYCOR, which is
96% silica. However, remember that the shortest UV is the most damaging to the skin and cells. Sunburn is caused by UV below 180 nm and UV near the visible light region, around 350-400 nm. UV lamps with quartz lenses transmit the longer UV wavelengths, causing the skin to redden. The atmosphere, luckily for us, blocks most of the short wavelength UV (remember ozone?). I hope this answers your question.
Answered by: Raymond Stackon, B.S. Physics, City College of N.Y.
'The strength and weakness of physicists is that we believe in what we can measure. And if we can't measure it, then we say it probably doesn't exist. And that closes us off to an enormous amount of phenomena that we may not be able to measure because they only happened once. For example, the Big Bang. ... That's one reason why they scoffed at higher dimensions for so many years. Now we realize that there's no alternative... '