Ethan Clarke
Newton's Rings are a phenomenon in optics, where interference patterns of light and dark-coloured concentric rings are observed between two pieces of glass, one convex and one flat. This phenomenon is caused by the interference of light waves, which create bright patterns when their crests coincide and destroy light when their troughs and crests meet. Newton's Rings have been observed in plastic as well, where the plastic from an insert touches the plastic of a holder, creating a similar effect. Anti-Newton Ring glass is made with an etched side that prevents Newton's Rings from forming, and non-glare acrylic is a cheaper alternative to this.
| Characteristics | Values |
|---|---|
| Phenomenon | Newton's rings |
| Type | Optical phenomenon |
| Cause | Interference of light waves between two surfaces |
| Appearance | Concentric light and dark-coloured bands |
| Surfaces Involved | One convex and one flat surface in contact at the centre |
| Light Type | Monochromatic light creates distinct alternating rings; white light produces a rainbow pattern |
| Application | Testing uniformity of polished surfaces |
| Prevention | Use of anti-Newton Ring glass or non-glare acrylic |
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What You'll Learn
Newton's Rings are an optical phenomenon
When light passes through the top piece of glass, it refracts off the bottom and top surfaces, resulting in a superposition of two rays. The ray reflecting off the bottom surface of the glass undergoes a 180-degree phase shift due to the difference in refractive indices of air and glass. This interference of light waves creates a pattern of bright and dark lines or bands called "interference fringes". These fringes are similar to contour lines on maps, with the gap between the surfaces being constant along a fringe. The phenomenon can also be observed when light passes through the flat surface of a plastic holder and onto a slightly concave plastic sleeve, as seen in some card protectors and PSA holders.
Monochromatic light creates distinct alternating rings, while white light produces a rainbow-coloured pattern. This is because the different wavelengths of light interfere at different thicknesses of the air layer between the surfaces. The radial position of the fringe pattern appears as a "rainbow" when the light is not monochromatic. The phenomenon can be used to test the uniformity of a polished surface by studying the interference pattern created when placed in contact with a perfectly flat glass surface.
Newton's Rings have been explained using the theory of waves of light. The air film between the glass sheet and lens has varying thicknesses, and reflection and refractive rays occur simultaneously when a ray strikes the lens surface. Rays that are refracted undergo a 180-degree phase change on reflection when they strike a glass sheet. Constructive interference occurs when the path difference between two waves is equal to an odd multiple of half a wavelength, while destructive interference occurs at even multiples.
To prevent Newton's Rings from forming, Anti-Newton Ring (ANR) glass can be used. However, it tends to be expensive, and some have suggested that non-glare acrylic is a cheaper and effective alternative.
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They are caused by light interference
Newton's rings are a phenomenon in optics, named after the English mathematician and physicist Sir Isaac Newton, who first investigated them in 1666. Newton's rings are a series of concentric light and dark-coloured bands observed between two pieces of glass when one is convex and rests on its curved side on another piece with a flat surface. This creates a layer of air between the two pieces of glass.
The phenomenon is caused by light interference, i.e., the superimposing of light waves. When the crests of the waves coincide, the light brightens, and when the trough and crest meet, the light is destroyed. The light waves reflected from both the top and bottom surfaces of the air film between the two pieces of glass interfere, creating a pattern of bright and dark lines or bands called "interference fringes". These fringes are similar to contour lines on maps, revealing differences in the thickness of the air gap. The gap between the surfaces is constant along a fringe.
The interference fringes form concentric rings because the gap between the glasses increases radially from the centre, where the two pieces of glass make contact. The path length difference between two adjacent bright or dark fringes is one wavelength λ of light, so the difference in the gap between the surfaces is half a wavelength. Since the wavelength of light is so small, this technique can measure very small departures from flatness. For example, the wavelength of red light is about 700 nm, so the difference in height between two fringes is 350 nm, about 1/100 the diameter of a human hair.
Newton's rings can also occur when light passes through the flat surface of a plastic holder and onto a slightly concave plastic sleeve, as in the case of PSA holders protecting small items such as cards and stickers. The plastic from the insert touching the plastic of the holder creates the effect, resulting in what looks like a moisture spot within the holder, even though it is completely free of moisture.
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Newton's Rings can be seen on plastic
Newton's Rings are a phenomenon in optics where a series of concentric light and dark-coloured bands are observed between two pieces of glass, one of which is convex and rests on its curved side on the other piece, which has a flat surface. This creates a layer of air between the two pieces of glass, with the gap increasing with radial distance from the centre. When viewed with white light, the different wavelengths of light interfere at different thicknesses of the air layer, resulting in a concentric ring pattern of rainbow colours. This phenomenon is caused by the interference of light waves, where the superimposing of waves results in brightened light when their crests coincide, and darkened light when the trough and crest meet.
Newton's Rings can be observed on plastic, as seen in the example of PSA holders used to protect small items such as cards and stickers. In this case, the Newton's Rings occur when light passes through the flat surface of the holder and onto the slightly concave sleeve inside. The plastic from the insert touches the plastic of the holder, creating the effect of Newton's Rings. This effect can be mitigated by using non-glare acrylic as an alternative to anti-Newton Ring glass, which is cheaper and provides excellent sharpness without the formation of Newton's Rings.
The phenomenon was first described by Robert Hooke in his 1665 book "Micrographia" and was further studied by Sir Isaac Newton in 1666 during the Great Plague. Newton's analysis of the phenomenon was published in his treatise "Opticks" in 1704, and the rings were subsequently named in his honour. The formation of Newton's Rings can be explained by the theory of waves of light, where reflection and refractive rays occur simultaneously when a ray strikes the lens surface, resulting in a phase change of 180° on reflection when they strike a glass sheet. This interference of light waves creates the alternating bright and dark rings characteristic of Newton's Rings.
In summary, Newton's Rings can indeed be observed on plastic surfaces, and this effect has been noticed in certain applications such as card and sticker holders. While anti-Newton Ring glass is available to prevent this phenomenon, non-glare acrylic has been suggested as a cheaper and effective alternative that eliminates Newton's Rings while also improving overall sharpness.
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Anti-Newton Ring glass exists
Newton's rings are a phenomenon observed when two flat optical surfaces are in close proximity, causing interference effects. This results in a pattern of bright and dark lines or bands called "interference fringes" that are similar to contour lines on maps. Newton's rings can be seen when a very slightly convex curved glass is placed on an optical flat glass, or when light passes through the flat surface of a plastic holder onto a slightly concave plastic sleeve.
Anti-Newton Ring (ANR) glass exists and is used to prevent the formation of Newton's rings. It is lightly etched on one side to deform the surface enough to prevent the interference effects, while still maintaining image quality. ANR glass is commonly used in scanners and film enlargers to scan photography negatives without the appearance of interference rings.
ANR glass is available for purchase from various suppliers, including online retailers and specialty optics companies. It can be cut to specific shapes and sizes to suit individual applications. Some users have reported success in using regular etched glass from frame glass shops as a more affordable alternative to ANR glass for film scanning.
When using ANR glass, it is important to ensure that the matte side of the glass is placed against the film or negative to effectively eliminate Newton's rings. Scanning at multiple resolutions may also be necessary to optimize image quality and reduce interference effects.
In addition to ANR glass, other methods can be employed to minimize Newton's rings. For example, in the context of card and sticker holders, inserts or sleeves may be used to create a slight curvature that prevents the formation of Newton's rings.
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Newton's Rings were first described by Robert Hooke
Newton's rings are a phenomenon in which an interference pattern is created by the reflection of light between two surfaces—usually a spherical surface and an adjacent flat surface. The phenomenon is named after Sir Isaac Newton, who studied it in 1666 while sequestered at home during the Great Plague. Newton recorded his observations in an essay titled "Of Colours".
However, the phenomenon was first described by Robert Hooke in his 1665 book *Micrographia*. Newton and Hooke had a dispute over the nature of light. Newton argued for a corpuscular nature of light, while Hooke favoured a wave-like nature. Newton did not publish his analysis until after Hooke's death in 1704, as part of his treatise "Opticks".
Newton's rings appear as a series of concentric, alternating bright and dark rings when viewed with monochromatic light. When viewed with white light, the rings form a concentric pattern of rainbow colours because the different wavelengths of light interfere at different thicknesses of the air layer between the surfaces. This interference results in a pattern of bright and dark lines or bands called "interference fringes" that are similar to contour lines on maps.
Newton's rings can be observed in various contexts, including in thin films of oil on water, soap bubbles, and the encapsulation of cards and stickers in plastic sleeves.
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Frequently asked questions
Newton's Rings are a series of concentric light and dark-coloured bands that occur due to light interference between two surfaces — a convex lens and a flat glass plate.
Newton's Rings can occur on plastic when light passes through the flat surface of a holder and onto a slightly concave sleeve. The plastic from the insert touching the plastic of the holder creates the effect.
Newton's Rings are caused by the interference of light waves. When crests coincide, the light brightens, but when the trough and crest meet, the light is destroyed.
Anti-Newton Ring (ANR) glass is made with an etched side that prevents Newton's Rings from forming. Non-glare acrylic is a cheaper alternative to ANR glass that also prevents Newton's Rings from forming.
