What is Glass: Definition and 656 Discussions

Glass is a non-crystalline, often transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of the molten form; some glasses such as volcanic glass are naturally occurring. The most familiar, and historically the oldest, types of manufactured glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. Soda-lime glass, containing around 70% silica, accounts for around 90% of manufactured glass. The term glass, in popular usage, is often used to refer only to this type of material, although silica-free glasses often have desirable properties for applications in modern communications technology. Some objects, such as drinking glasses and eyeglasses, are so commonly made of silicate-based glass that they are simply called by the name of the material.
Although brittle, buried silicate glass will survive for very long periods if not disturbed, and many examples of glass fragments exist from early glass-making cultures. Archaeological evidence suggests glass-making dates back to at least 3,600 BC in Mesopotamia, Egypt, or Syria. The earliest known glass objects were beads, perhaps created accidentally during metalworking or the production of faience. Due to its ease of formability into any shape, glass has been traditionally used for vessels, such as bowls, vases, bottles, jars and drinking glasses. In its most solid forms, it has also been used for paperweights and marbles. Glass can be coloured by adding metal salts or painted and printed as enamelled glass.
The refractive, reflective and transmission properties of glass make glass suitable for manufacturing optical lenses, prisms, and optoelectronics materials. Extruded glass fibres have application as optical fibres in communications networks, thermal insulating material when matted as glass wool so as to trap air, or in glass-fibre reinforced plastic (fibreglass).

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  1. E

    Table tempered glass edge break pattern

    Supposed someone (like a naughty child) sits on the edge of the cantilevered hardened tempered glass table (see photo below) and it breaks. Would all the table glass break into pieces at same time or would the edge break separately? and would there still be sharp edges? I know tempered glass...
  2. sbrothy

    Serious science is alive and well....

    Don't let anyone tell you otherwise. Optimizing Beer Glass Shapes to Minimize Heat Transfer During Consumption.
  3. dzbshea

    My glass beer bottle survived a fall from the 10th floor, how, & why?

    All of you sound really smart, I have a question for you. This happened in Hawaii, years ago. I was drinking with my highschool friends, we decided who can throw the empty brown Budweiser bottles (the short stocky kind) the furthest from the balcony 10 flights down would go get another round. I...
  4. U

    I If centrifugal force doesn't exist, why does a glass move outward in the fridge door?

    If centrifugal force dont exist why glass of water moves outward/toward me when I open fridge door? Glass of water moves out in relation to door and in relation to earth, so what force push glass out?
  5. Pushoam

    B Pressure of air inside a glass

    Let's consider an uncovered glass. Air particles are present in the glass. $$ P_1 = P_a$$ $$P_2 =P_1 +\rho gh = P_a +\rho g h$$where ##P_A## is atmospheric pressuere and ##\rho ## is air density. Now, if I cover the glass with a plastic card, then what is ## P_1##? $$P_2 =P_1 +\rho gh $$ 1)...
  6. orangephysik

    Glass prism and its refractive index

    Hi, I've attached the photo of the diagram, a photo of my drawings on the diagram. for a): Since the prism is an equalateral triangle, all angles inside the prism is 60°. This means the angle adjacent to α is 180° - 60° = 120°, which means the last angle is 180° - 24.5° - 120° = 35.5°. The...
  7. J

    I Interaction of EM radiation with Glass

    Hi, I wanted some clarification on the mechanism for how EM radiation interacts with standard glass, namely IR, visible and high energy (UV and X-ray). Looking online most sources seem to say the band gap is around 10eV. Since visible light is about 1-3eV visible light will be transmitted. IR...
  8. S

    I How bad is this article about uranium glass?

    https://getpocket.com/explore/item/these-people-love-to-collect-radioactive-glass-are-they-nuts It talks about uranium giving off "alpha waves/rays" & "beta waves/rays", and an isotope of U-308. My understanding is that alpha & beta radiation is particle in nature whereas gamma radiation is a...
  9. M

    I Light coupling from optical fiber to glass?

    Hey everyone, I am trying to couple light from an optical fiber connected to an LED (365nm) into a small glass capillary which is pulled on one end and should be used as a small light source. The idea is to use the glass as a light guide. Has anyone tips for efficient incoupling of the light? I...
  10. MatinSAR

    Buoyant force acting on an inverted glass in water

    My answer : According to the question, the glass and the air inside it entered the water. Let's assume that the net force becomes zero at a moment, that is, the sum of the weight force and F is equal to the buoyancy force. By going down in the water, the gas volume decreases, so the buoyancy...
  11. C

    I Why didn't the wrecking ball smash his head?

    [Mentor Note -- post appears to have been edited based on post #2] Hello everyone! I was watching a Walter Lewin lecture and saw him do something very dangerous, he released a wrecking ball at a certain height from the ground, upon returning the ball did not smash his head. If you watch the...
  12. P

    B Can a Planet Made of Glass Generate Free Energy?

    As far as I know, if vacuum antigravitates, it makes the light that travels through it redshift, e.g. in a very large empty box with mirror walls, light will just lose energy. I am interested in the reverse effect, if we had a very large box or planet with mirror walls, that is filled with...
  13. H

    I Group velocity for an electromagnetic wave inside glass

    Hi, I saw that the group velocity for an electromagnetic wave can be calculate with the following formula ##v_g = v_p + k \frac{d v_p}{dk}## Thus, since ##v_p = \frac{c}{n} = \frac{\omega}{k}## Is it correct to say that ##v_g = \frac{c}{n} + k(- \frac{\omega}{k^2})## where ##k =...
  14. Astronuc

    In Medieval Africa, A Unique Process for Purifying Gold With Glass

    Medieval Africans Had a Unique Process for Purifying Gold With Glass And scientists in Illinois have recreated it. https://www.atlasobscura.com/articles/medieval-african-gold Mansa Musa, emperor of Mali from 1312 to 1337, was widely known for his vast wealth in the form of gold deposits...
  15. yglo98

    Optics. A laser beam is refracted in a piece of glass.

    A red laser with the diameter of 3mm is directed towards a piece of glass. It has the effect, P of 1mW. The angle of incidence is 90 degrees. The glass has refraction index n2= 1,5 and thickness 2 cm. Its front side is convex with a convergence radius,R, of 11 cm. The back side is plane. Whats...
  16. Physics Slayer

    Boiling a glass of water in a bowl of water - tricky question?

    I think the water in the bowl of water will boil first because the glass won't conduct the heat instantaneously, and hence the water in the glass will boil after the water in the bowl. Is this correct? I am guessing this is a trick question and the water in both boil at the same time, but I...
  17. informerkh

    Optical qualities of prism sheet and glass substrate (LCD screen)

    Hi! I am an electronics engineer and I would be very grateful for some help and suggestions with my problem. I am experiencing severe discomfort when working with almost any LCD screen (smartphones, laptops, monitors). Ophthalmologists say that I am completely healthy and they cannot understand...
  18. Stryker331

    Understanding Spark Production in Dissectable Glass Capacitors

    I think a high enough voltage may have permanently polarized the glass.
  19. Astronuc

    Mysterious Shards of Glass Strewn Across Miles of Atacama Desert

    A mysterious field of glass fragments, scattered across Chile's Atacama Desert, and aligned in a vast corridor stretching 75 kilometers long (almost 50 miles). They first came to scientists' attention about a decade ago...
  20. LCSphysicist

    Inside glass, can I apply relativity of speed for light?

    I was doing a exercise which considerst he time it takes for light travels a glass with thickness proper D and velocity v. The speed of light is c/n inside the glass. Now, my approach was to go to the glass frame, take the relative speed between the glass and the light using the trivial formula...
  21. V

    Reason for glass rod losing electrons

    I am not sure if the explanation below is enough. This is a high school level question. When rubbing occurs between glass and silk, then heat energy is produced which provides the energy needed to free up electrons in outermost orbits of atoms in silk or glass. But silk has very tightly bound...
  22. Tech_Rizzle

    I Amount of Noise extinction in Acrylic glass per thickness in mm

    Hey guys, I need your help with the following topic on which I couldn't find sufficient information on the internet to solve. In the need to further insulate my velux roof swing window against against airborne motor and tire sound from the nearby street, I came across the idea to install an...
  23. phyduck

    Chemical/Paint Removal of broken glass from solar panel

    I'm looking to find a way to remove tempered glass that has been shattered from solar panels to make them viable once again. I have no idea what kind of adhesive is used here, but I imagine it is some sort of epoxy. I've tried to peel it off with a pressure washer at the car wash to no avail...
  24. H

    A slab of glass dielectric is inserted into a parallel plate capacitor

    I use the following equations to understand this question/answer. First, C = k(ε*Area)/distance = Q/V = Q/ (E*distance) As a slab of glass is added, k increases and thus E decreases. F=QE, as E decreases, force decreases as well. How does this relate to the 'force attracts the glass into the...
  25. D

    What to fill a glass bottle with (a liquid that hardens) to lower its volume?

    Homework Statement:: Oil Lamp ( Paraffin help ) Relevant Equations:: Not sure what to write here HI folks, I'm trying to make an oil lamp from an old Vodka bottle. The bottle is the usual 750ml and is in a skull shape bottle. ( maybe you know it ) Anyhow I have all the materials and almost...
  26. B

    Glass Thermal Energy: Solid Glass Beam w/ Spiral Column

    Could I put this on here for answers please ? If produced a solid glass beam with a spiral column thorough the middle of it would the core be hotter or cooler than the surrounding air? If colder could it be use in conjunction with ground source technology to produce hot water? I not sure how to...
  27. core1985

    Very Important Question Regarding Embroidery and Magnifying glass

    I want to ask that if i use light head magnifying glass is it safe? For embroidery or an idea came to my mind that why not I use Webcam and a big display like 23 inch and then focus webcam on my embroidery and see on my LCD I have also reflector glasses to avoid eye strain totally ? . Because in...
  28. richengle

    How does the speed of light change when it enters glass?

    its has been said that light slows down in glass, but some talk about phase velocity and group velocity... then there is the velocity of the photons, which some say is always c. What are those speeds [Vgroup, Vphase, Vphoton, Vlight] in glass, and what do they mean?
  29. richengle

    Can Light Travel Faster Than the Speed of Light in Glass?

    i made a simulation of waves in glass and in air. my simulation has led me to believe that if light begins in glass, it can travel to the air, and then move much faster, and then go back into the glass at a point further down. Could this happen in real life? here is the video of my...
  30. G

    Bubbles in a falling glass of champagne

    Suppose you just poured a glass of champagne, then you drop the glass straight down (so that there is no tilting). Do the bubbles: (1) Continue to rise with respect to the glass. (2) Remain in place with respect to the glass. (3) Sink with respect to the glass.My intuition is telling me that...
  31. B

    Glass bottle with a prolonged neck that continues into the inner space

    Is it possible to create following two shapes from glass using currently known glass mass production techniques? Shape #1: bottle with a prolonged neck that continues into the inner space, like this (cross section): | | | | /| |\ / | | \ / \ / \ | | |...
  32. J

    Can a Cracked LCD Glass be Repaired or Should I Just Buy a New Clock?

    I have a small LCD clock and a corner of the LCD glass cracked and separated. This small region of the glass lines up with one of the pads on the circuit board and the result is that one of the segments is non-operative. I look at the LCD glass and I can't see any sort of circuit trace. Is the...
  33. Leo Liu

    Pulling a tablecloth from under a glass

    The question is stated above. I tried to solve it on my own and I obtained the following three questions: $$\begin{cases} a_{cloth}=\frac{F-\mu mg} M\\ \\ a_{glass}=\frac{\mu mg}m=\mu g \end{cases}$$ Where small m is the mass of the glass and capital M is the mass of the cloth. However, the...
  34. S

    Interference pattern for two glass plates closely separated and tilted

    hi, i know you have to use 2t/lambda= m/2 to get the answer of 10.9 um. However i was taught that there would be phase difference caused by reflection, since n1(air)< n2(glass). SO the equation in my head would be 2t/lambda - 1/2= m/2. Can someone explain why I'm wrong?
  35. B

    Heat distribution in a piece of glass receiving protons

    First of all, I didn't know whether to pick this subforum or the engineering/compsci one, I understand this might need to be moved to a more appropriate subforum. The general approach is fairly obvious, use implicit method to construct the tridiagonal matrix for Thomas method and solve. However...
  36. Zohar

    B Why does coffee in a glass leaves its signatory on the surface?

    Some of us may use coffee coaster for our drinks. I was always wondering about that phenomenon and failed to find something on the net yet.
  37. pimpypot

    Wood/Glass/Metal Where to Find Uranium Glass Beads/Wands & Safety Protocols

    I cannot find a source of uranium glass beads/wands for art making. It is mentioned online that one can make UV glass with a derivative of uranyl nitrate, UO2(NO3)2 . Does anyone know a source of uranyl nitrate, or raw glass material, and what are the minimum safety protocols, such as...
  38. S

    B Glass in flatbed scanner transparent to UV-C (~254nm)?

    Hello, I am making a DIY UV-C germicidal box as part of my defense-in-depth strategy for protecting my household but I am having trouble determining whether a particular plate of glass that I have will be transparent to UV in the 250-280nm range. The glass in question is from a flatbed scanner...
  39. Amitayas Banerjee

    How does water rise along a glass plate? (surface tension question)

    So, I was studying about general properties of matter and topics like surface tension. I came across the phenomenon of water rising along a glass plate like in the picture. I looked for some mathematical interpretation of this on the internet and in some books. [![enter image description...
  40. C

    Which Orientation is Worse for Leakage in a Glass Bottle?

    Hi, I'm looking for help in knowing which orientation is worse for finding leakage: upside down, sideways or no difference. I have a 30ml glass bottle filled with 26ml of oil that is closed with a glass stopper (cork) applied with a set force. The neck of the bottle is filled with oil when...
  41. jisbon

    Light rays passing through a glass prism

    Hi all! Breaking down the question bit by bit: AC is coated with a silver film which acts as a mirror - Okay, nothing as of yet right..? A light beam is an incident onto prism at Point Q such that angle PQB is 40 degrees - This means that my incident angle is 50 degrees as shown below...
  42. L

    I What is the behavior of photons inside glass?

    I'm aware of the numerous threads on the subject "light inside glass" there have been in the past, in case you will indicate me an appropriate one, but I haven't been able to find a clear answer to the questions: 1) Do photons really exist inside a (homogeneous, linear, transparent, refracting...
  43. B

    Is Transparent Aluminum the Next Big Breakthrough in Glass Technology?

    This link makes me fondly remember the goofy Star Trek to save the Blue Whales and how Scotty invented something he invented in the future with the help of Spock. Transparent Aluminum https://phys.org/news/2019-11-aluminum-lasers-bendable-glass.html
  44. mastermechanic

    How to reflect light through a glass like those in holographic sight?

    Hello everyone, Most of you know the Holographic Sights used on weapons to aim. I have a 3d printer and I will try to replicate one of them. I just wonder how the red dot/sight is reflected on the glass without making the light reflected anywhere else? It doesn't have to have exact same...
  45. G

    A glass and bottle of water moving on their own

    Hi all. I'm a bit confused. I was lying in bed last night - on one side of a very big bed, not moving. When all of a sudden I heard a big crashing sound of things moving and falling. I switched the light on and on the bedside cabinet on the opposite side to me, a half full bottle of water and a...