How to Bend A Diamond

by Adwaith.B.S(2016-2019)

adwaithbalachandran123@gmail.com

 

Diamond is the hardest natural material, but now scientists have shown that it can bend and stretch, much like rubber, and even elastically snap back into shape — even if it only happens with diamonds that are very small. Such flexibility could open up a wide new range of applications for diamond, the researchers say.

Diamond is extraordinarily hard, meaning it excels at resisting any change to its shape — that’s why a diamond can cut through softer materials and will only be scratched by another diamond. However, diamond is not especially tough — when enough force is applied to it to change its shape, it doesn’t usually bend, it breaks.

Bend Like A Diamond

Still, previous research found that, in theory, the diamond should be able to flex a bit. The key was to create pure crystals of diamond without any microscopic flaws or variations that would make them brittle.

An international team of researchers took thin films of artificial diamonds and etched out needles just 300 nanometers, or billionths of a meter, long.. They next pressed down on these slivers with a diamond probe and watched what happened using a scanning electron microscope.

The scientists found their diamond needles could bend and stretch by up to 9 percent without breaking and rebound back to their original shape after the pressure was removed. These results approach what the research team’s computer models suggested was the diamond’s theoretical limit of flexibility. By contrast, an ordinary diamond in bulk form breaks well below strain levels of even 1 percent.

“The hardest natural material, diamond, which is commonly believed to be undeformable, can be bent and stretched significantly,” said study co-senior author Yang Lu, a materials scientist and mechanical engineer at the City University of Hong Kong. “A diamond needle could be severely bent almost 30 degrees and, more importantly, fully recover.”

Mind-bending

The unexpected improved durability of diamond could lead to many new applications. For instance, robust and cost-effective microscopic diamond needles could help deliver genes or drugs into cells, Lu said.

In addition, when a diamond is flexed, it could stretch and squeeze the molecular bonds in ways that could significantly alter its electronic, thermal, optical, magnetic and chemical properties, said study co-senior author Subra Suresh, president of Singapore’s Nanyang Technological University. The researchers suggested that further experiments flexing diamond might discover new behaviors for novel applications, “such as a more powerful or colorful laser or maser,” Lu said.

Controlling how sensitive diamonds are to magnetic fields could also have a variety of sensor applications, said study co-senior author Ming Dao, a materials scientist and mechanical engineer at MIT. For example, a diamond with altered magnetic properties could find use in magnetic resonance imaging (MRI) scans.

The scientists detailed their findings in the April 20 issue of the journal Science.

Optics

by Adarsh S.M(2016-2019)

https://www.facebook.com/adarsh.asm.7

Optics is the branch of physics which involves the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it.^[1] Optics usually describes the behaviour of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.

Most optical phenomena can be accounted for using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice. Practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics. Historically, the ray-based model of light was developed first, followed by the wave model of light. Progress in electromagnetic theory in the 19th century led to the discovery that light waves were in fact electromagnetic radiation.

Some phenomena depend on the fact that light has both wave-like and particle-like properties. Explanation of these effects requires quantum mechanics. When considering light’s particle-like properties, the light is modelled as a collection of particles called “photons“. Quantum optics deals with the application of quantum mechanics to optical systems.

Optical science is relevant to and studied in many related disciplines including astronomy, various engineering fields, photography, and medicine (particularly ophthalmology and optometry). Practical applications of optics are found in a variety of technologies and everyday objects, including mirrors, lenses,telescopes, microscopes, lasers, and fibre optics.

IRIDESCENCE

by Anaswara.J.S.(2016-2019)

anaswarajs@gmail.com

Iridescence (also known as
goniochromism ) is the phenomenon of certain surfaces that appear to
gradually change colour as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles , butterfly wings and sea shells , as well as certain minerals. It is often created by
structural coloration (microstructures that interfere with light).
When light encounters boundaries between media that differ in refractive index, structural coloration can be produced by interference, diffraction or scattering. Both interference and diffraction can produce iridescent colours that change in appearance with viewing geometry, and are characterized by single or multiple reflectance maxima. Interference colours are produced when light interacts at boundaries of media with different refractive indices, where, depending on the dimensions of the media, some wavelengths constructively interfere to produce brilliant colours, while the remaining wavelengths destructively interfere . Interference-based colours can be produced by optical materials arranged in simple thin films or in multilayer reflectors. Diffraction gratings are reflective surfaces with regularly ordered parallel grooves or depressions that disperse different wavelengths of light in different directions, which, in turn, depends on the periodicity of the grating and its relation with incident wavelengths . Colour-producing nanostructures that are arranged in a crystalline pattern can also produce iridescence through diffraction following Bragg’s law . Diffraction and interference mechanisms can be combined to produce complex optical effects, as in the scales of some butterfly wings.

Some forms of scattering produce non-iridescent structural colours that tend to reflect maximally at shorter wavelengths ranging from ultraviolet to turquoise, although there are examples of long-wavelength structural colours produced by scattering . Non-iridescent structural colours in animals were long thought to be produced by incoherent scattering mechanisms such as Rayleigh scattering and Tyndall scattering . However, recent work by Prum and colleagues suggests that many, if not most, non-iridescent structural colours in animals are produced by the constructive interference of light . Thus, although iridescent and non-iridescent structural colours were assumed to involve fundamentally different mechanisms, it is becoming increasingly clear that both types of colour can result from coherent scattering, and that the main difference between them results from differences in the organization of their colour-producing nanostructures . Because non-iridescent structural colours are produced by quasi-ordered arrays instead of layered or crystalline structures, they tend to be less saturated, more diffuse and unaffected by viewing geometry. Nevertheless, it is sometimes difficult to distinguish between iridescent and non-iridescent colours, since structural colours often involve multiple scales of organization . It should also be noted that incoherent scattering can produce whiteness by scattering all visible wavelengths. For the purposes of this review, we interpret iridescence in its broadest sense, meaning colours that change in hue or intensity with viewing geometry.

UNIQUE FEATURES OF IRIDESCENT VISUAL SIGNALS

1. Directionality

Iridescent colours are by definition highly directional. Changes in viewing geometry can dramatically alter the appearance of iridescent colours, producing considerable changes in hue, intensity or both

2. Maximizing conspicuousness

Another unique feature of iridescent colours is that, depending on the underlying mechanism and viewing geometry, they can be exceptionally bright and saturated to a degree that is not usually achieved by pigment-based colours

3. Short-wavelength colours

Another important feature of iridescent signals, as well as other structural colours, is that they provide animals with the ability to produce colours reflecting maximally or secondarily at short wavelengths ranging from blue to ultraviolet.

4. Environmental variation

Another feature that sets iridescent colours apart from pigment-based colours is that their hue, saturation and brightness are directly dependent on the dimensions and refractive indices of the colour-producing nanostructures. Nanometre-scale differences in either of these characteristics can cause dramatic variation in colour both across species .

Iridescence in Butterfly Wings

When light hits the different layers of a butterfly wing, it is reflected numerous times. The combination of all these reflections causes the intense colours of many species.