Optics

Like all the different types of light, the spectrum of visible light is absorbed and emitted in the form of tiny packets of energy called as photons. These photons have both the properties of a wave as well as a particle. Hence this type of property is called as wave–particle duality and the study of light in the area of physics is known as Optics.

Optics is a branch of physics that deals with the determination of behavior and the properties of light, along with its interactions with the matter and also with the instruments which are used to detect it. Optics, in a simple manner, is used to describe the behavior of visible light, infrared light, and the ultraviolet. Imaging is done with the help of a system called as an image forming an optical system.

Light and its Optical properties

Light is a form of energy which is in the form of an electromagnetic wave and is almost everywhere around us. The visible light has wavelengths measuring between 400–700 nanometres. Sun is the primary source of light by which plants utilize this to produce their energy.

In physics, the term light also refers to electromagnetic radiation of different kinds of wavelength, whether it is visible to the naked eye or not. Hence by this, the gamma rays, microwaves, X-rays and the radio waves are also types of light. Light exhibits various properties which are given below-

• Reflection- Reflection is one of the primary properties of light. Reflection is nothing but what you see the images in the mirrors. Reflection is defined as the change in direction of light at an interface in-between two different media so that the wave-front returns into a medium from which it was originated. The typical examples for reflection of light include sound waves and water waves.
• Speed of light- The rate at which the light travels in free space is called as Speed of light. For example, the light travels 30% slower in water when compared to vacuum.
• Refraction- The bending of light when it passes from one medium to another is called as Refraction. This property of refraction is used in a number of devices like microscopes, magnifying lenses, corrective lenses, and so on. In this property, when the light is transmitted through a medium, polarization of electrons takes place which in-turn reduces the speed of light, thus changing the direction of light.
• Total internal reflection- When a beam of light strikes the water, a part of the light is reflected, and some part of the light is refracted. This phenomenon is called as Total internal reflection.
• Dispersion- It is a property of light, where the white light splits into its constituent colors. The phenomenon of dispersion can be observed in the form of a prism.

The other properties of light include diffraction and interference. So, what you observe when, you look out at the beautiful scenario? Whether the light gets reflected, dispersed, refracted, internally reflected or diffracted.

Applications of Optics

The properties of optics are applied in various fields of Physics-

• The refraction phenomenon is applied in the case of lenses (Convex and concave) for the purpose of forming an image of the object.
• Geometrical optics is used in studying of how the images form in an optical system.
• In medical applications, it is used in the optical diagnosis of the mysteries of the human body.
• It is used in the therapeutical and surgeries of the human tissues.

(Source: byjus)

Space Research

Space Science is the study and exploration of anything and everything to do with whatever is out there beyond Earth’s immediate influence. Here I am ignoring the fact that Earth’s gravitational influence stretches a long long way beyond our atmosphere.

Space Science includes disciplines of astronomy (studying things in space by remote observation and data) and aerospace engineering (reaching out into space for exploiting its resources, using its location advantages, and gathering data on celestial objects).

Earth is so small that whatever science has achieved until now is a tiny (tending to zero) part of the possibilities of science. The rest is out there, in space, to observe, understand, discover, and invent for. In the timeline of science we haven’t even taken the first full step since humans starting walking on Earth.

We still have to understand most of:

·         How the universe was formed and how it works

·         What’s on the other planets, stars, galaxies, star systems, and everything between them

·         How and why the objects in the universe were formed and how they interact

·         Life beyond Earth

·         The possibilities of traveling in space and our limits for it

·         How objects in space affect us in the short and long term

·         …

(Ref: Prashant Dobriyal)

3D Printing technology

What is 3D printing?

3D printing or additive manufacturing is a process of making three dimensional solid objects from a digital file. The creation of a 3D printed object is achieved using additive processes. In an additive process an object is created by laying down successive layers of material until the object is created.  Each of these layers can be seen as a thinly sliced horizontal cross-section of the eventual object.

How does 3D printing work?

It all starts with making a virtual design of the object you want to create. This virtual design is for instance a CAD (Computer Aided Design) file. This CAD file is created using a 3D modeling application or with a 3D scanner (to copy an existing object). A 3D scanner can make a 3D digital copy of an object.

Types of 3D printers or 3D printing technologies overview

Stereolithography is a 3d printing method that can be used to implement your projects that involve 3D printing of objects. Although this method is the oldest one in history of 3D printing it’s still being used nowadays. The idea and application of this method are amazing. Whether you are a mechanical engineer, who needs to verify if the part can fit to your design, or creative person who wants to make a plastic prototype of new coming project, Stereolithography can help you to turn your models into a real 3D printed object.

Fused deposition modeling (FDM) technology was developed and implemented at first time by Scott Crump, Stratasys Ltd. founder, in 1980s. Other 3D printing companies have adopted similar technologies but under different names. With help of FDM you can print not only functional prototypes, but also concept models and final end-use products. What is good about this technology that all parts printed with FDM can go in high-performance and engineering-grade thermoplastic, which is very beneficial for mechanic engineers and manufactures.

Laser Sintering (SLS) is a technique that uses laser as power source to form solid 3D objects. This technique was developed by Carl Deckard, a student of Texas University, and his professor Joe Beaman in 1980s. Later on they took part in foundation of Desk Top Manufacturing (DTM) Corp., that was sold to its big competitor 3D Systems in 2001. As was stated previously, 3D systems Inc. developed stereolithography, which in some way is very similar to Selective Laser Sintering. The main difference between SLS and SLA is that it uses powdered material in the vat instead of liquid resin as stereolithography does.

(Ref: Jasmine Thompson)

What is Plasma, what are its uses, and where does it come from?

What is plasma? Plasma is considered the 4th state of matter. Plasma is a cloud of protons, neutrons and electrons where all the electrons have come loose from their respective molecules and atoms. And it could reach up to a whopping 10,000 kelvins or 17000 degrees fahrenheit. Akshat Mahajan from BSc Physics UCLA says, “A plasma is any ionised (charged) gas. It doesn't have to be fully charged (i.e. completely stripped of all its atoms or completely ionised) - even partial ionisation is sufficient to call something a plasma.” What he is basically saying is the plasma can occur wherever a charge is missing. And plasmas can be quite beautiful. An aurora borealis mainly is solar wind flowing past the earth, and a solar wind is mainly made out of plasma, which is held by the earth's magnetic field.

Plasma is used in many applications. Plasma is used in television, neon signs and fluorescent lights. Stars, lightning, and some flames consist of plasma. ThoughtCo says, “More exotic sources of plasma include particles in nuclear fusion reactors and weapons, but everyday sources include the Sun, lightning, fire, and neon signs. “ Other examples of plasma include static electricity, plasma balls, and the ionosphere.

Most people know plasma from a popular film called star wars. More specifically the lightsabers they use to fight with. These blades, are made out of plasma powered by the fictional kyber crystal. Unfortunately, it is not very easy to create something with that power, knowing that it will take 20 megawatts or 20 million watts just to melt through through steel. And that can power about 14000 households before the battery goes out.

Overall plasma is a very extraordinary thing that most people don't know about. Some things people don't know about plasma it is a state of matter. Which is mainly because when taught in school they only learn the main three. Pluto.space.swri.edu says, “A plasma is a hot ionized gas consisting of approximately equal numbers of positively charged ions and negatively charged electrons. The characteristics of plasmas are significantly different from those of ordinary neutral gases that is why it is the 4th state of matter”.Therefore plasma is the 4th state of matter.

(Source: Neil Lapsia)

Acoustics

Acoustics is the science of sound and someone who studies acoustics is called an acoustician.

There are many kinds of sound and many ways that sound affects our lives. For example, we use sound to talk and sound is important for designing musical instruments, concert halls, surround sound stereo and hearing aids. Sound can also be used to find oil and gas, to study earthquakes and climate change, and to make sure that the baby in a mother’s womb is healthy. There are the sounds humans can hear, but there are also sounds that only some animals can hear, like a dog whistle.

There are a lot of different acoustics fields of study. If you study acoustics, you might study the production, control, transmission, reception, or effects of sound on people, animals or even objects.

Mathematical Biology

Mathematical and theoretical biology is a branch of biology which employs theoretical analysis, mathematical models and abstractions of the living organisms to investigate the principles that govern the structure, development and behavior of the systems, as opposed to biology which deals with the conduction of experiments to prove and validate the scientific theories. The field is sometimes called mathematical biology or biomathematics to stress the mathematical side, or theoretical biology to stress the biological side. Theoretical biology focuses more on the development of theoretical principles for biology while mathematical biology focuses on the use of mathematical tools to study biological systems, even though the two terms are sometimes interchanged.

Mathematical biology aims at the mathematical representation and modeling of biological processes, using techniques and tools of applied mathematics and it can be useful in both theoretical and practical research. Describing systems in a quantitative manner means their behavior can be better simulated, and hence properties can be predicted that might not be evident to the experimenter. This requires precise mathematical models.

Because of the complexity of the living systems, theoretical biology employs several fields of mathematics, and has contributed to the development of new techniques.

(Ref: Wikipedia)

Laser

How do laser engineers use physics?

We use geometric optics to design the optical resonator. We use wave optics to predict the performance of the laser and resonator.

Depending on the type of laser we may use chemical kinetics, gas dynamics, and other disciplines to predict the flow of gases in the gain medium. We may use solid state physics to model the gain medium.

We use quantum mechanics of molecules and quantum electronics to model the states involved in the energy process of pumping and extracting energy. We use thermal and statistical physics to determine how and by how much to cool the gain medium. We may make use of stimulated brillouin scattering to control the wavefront errors introduced by a non-homogeneous gain medium.

Once the beam exits from the resonator, we make use of interference to determine the wavefront error of the laser beam. We then make use of some fancy processing to calculate the best fit deformable mirror surface but avoiding unstable eigen modes that can latch up.

We use knowledge of diffraction to determine how large the beam must be expanded to propagate the distance we need to place a spot on a distant object.

We use knowledge of the atmospheric density statistics to determine the structure function along the propagating path to know how much wavefront aberration and scintillation we will get. If it is too much, we propagate additional laser beams along the path to remotely measure the atmospheric turbulence so that we can pre-correct for it.

We use computational fluid dynamics to determine the air flow around the laser telescope to minimize he impact on the laser beam.We have to use physics to determine how much laser signal we will get back and since it is not enough, ways to use the signal that we will get.

We may use Doppler shifting of the reflected laser beam to help determine how fast the object is moving. We may use short pulses and time of flight to determine how far away the object is. Rayleigh scatter theory helps determine if we will be able to detect where the beam is before it gets to the object of interest.

(Ref: Bill Otto)

Molecular Astrophysics

Molecular Astrophysics concerns the study of emission from molecules in space. Lew Snyder recently presented a list of the 110 currently known interstellar molecules. These molecules have large numbers of observable transitions. To find specific frequencies, try Herb Pickett's Molecular Spectroscopy Home Page or Frank Lovas' list of recommended rest frequencies. Tom Kuiper has put together an explanation of molecular radio spectroscopy for emission lines. Lines may also be observed in absorption--for example the highly redshifted lines seen against the gravitationally lensed quasar PKS1830-211.

High energy radiation, such as ultraviolet light, can break the molecular bonds which hold atoms in molecules. In general then, molecules are found in cool astrophysical environments. The most massive objects in our Galaxy are giant clouds of molecules and dust, creatively named Giant Molecular Clouds. In these clouds, and smaller versions of them, stars and planets are formed. One of the primary fields of study of molecular astrophysics then, is star and planet formation. Molecules may be found in many environments, however, from stellar atmospheres to those of planetary satellites. Most of these locations are cool, and molecular emission is most easily studied via photons emitted when the molecules make transitions between low rotational energy states. One molecule, comprised of the abundant carbon and oxygen atoms, and very stable against dissociation into atoms, is carbon monoxide, CO. The wavelength of the photon emitted when the CO molecules falls from its lowest excited state to its zero energy, or ground, state is 2.6mm, or 115 gigahertz (billion hertz). This frequency is a thousand times higher than typical FM radio frequencies. At these high frequencies, molecules in the Earth's atmosphere can block transmissions from space, and telescopes must be located in dry (water is an important atmospheric blocker), high sites. Radio telescopes must have very accurate surfaces to produce high fidelity images. NRAO pioneered development of accurate antennas and high frequency receivers, and the development of molecular astrophysics, with the 11m radio telescope. In 1982, the surface of the 11m was replaced with a much more accurate 12m surface.

(Ref: National Radio Astronomy Observatory)

Acoustics

Acoustics is defined as the science that deals with the production, control, transmission, reception, and effects of sound (as defined by Merriam-Webster). Many people mistakenly think that acoustics is strictly musical or architectural in nature. While acoustics does include the study of musical instruments and architectural spaces, it also covers a vast range of topics, including: noise control, SONAR for submarine navigation, ultrasounds for medical imaging, thermoacoustic refrigeration, seismology, bioacoustics, and electroacoustic communication.

(Ref: BYU Acoustics Research Group)

The perceptional capabilities of the human ear, three different frequency ranges are distinguished. The range of hearing stretches from about 16 Hz to 16 kHz. Lower frequencies are called infra-sound, higher frequencies are called ultra-sound.

The field of acoustics can be subdivided into several special topics such as:

Theoretical acoustics, Nonlinear acoustics, Underwater acoustics, Ultrasound, Vibrations, Noise control, Room acoustics, Building acoustics, Electroacoustics, Acoustics of the ear.

Speed of sound in air:

temperature [◦C]   | speed of sound c [m/s]

   0                                                                 331.3

                        10                                      337.3

                        20                                      343.2

Density of air at sea level:

temperature [◦C]   |  density of air ρ [kg/m3 ]

        0                                              1.292

     10                                               1.247

     20                                               1.204

Acoustic impedance:

temperature [◦C]   |   ρc [Ns/m3 ]

       0                                       428.0

    10                                       420.5

    20                                       413.3

(Ref: Kurt Heutschi)

Dark Matter Physics

Dark matter is composed of particles that do not absorb, reflect, or emit light, so they cannot be detected by observing electromagnetic radiation. Dark matter is material that cannot be seen directly. We know that dark matter exists because of the effect it has on objects that we can observe directly.

Dark matter may account for the unexplained motions of stars within galaxies. Computers play an important role in the search for dark matter data. They allow scientists to create models which predict galaxy behavior. Satellites are also being used to gather dark matter data. In 1997, a Hubble Space Telescope image revealed light from a distant galaxy cluster being bent by another cluster in the foreground of the image. Based on the way the light was bent, scientists estimated the mass of the foreground cluster to be 250 times greater than the visible matter in the cluster. Scientists believe that dark matter in the cluster accounts for the unexplained mass.

Scientists have produced many theories about what exactly dark matter may be normal objects such as cold gasses, dark galaxies, or massive compact halo objects (called MACHOs, they would include black holes and brown dwarfs). Other scientists believe that dark matter may be composed of strange particles which were created in the very early universe. Such particles may include axions, weakly interacting massive particles (called WIMPs), or neutrinos.

Understanding dark matter is important to understanding the size, shape and future of the universe. The amount of dark matter in the universe will determine if the universe is open (continues to expand), closed (expands to a point and then collapses) or flat (expands and then stops when it reaches equilibrium). Understanding dark matter will also aid in definitively explaining the formation and evolution of galaxies and clusters. As a galaxy spins it should be torn apart. This does not happen, so something is holding the galaxy together. The something is gravity; the amount of gravity required to do this, however, is enormous and could not be generated by the visible matter in the galaxy.

(REF: StarChild )

Photonics

Photonics is the generation, transmission, emission, modulation, switching and detection of light and utilization of light and other electromagnetic radiation. Photonics offers solutions to the global challenges of our time.  Apart from this, photonics includes all applications of light across the spectrum, ranging from ultraviolet to visible light. Photonics finds application across various application segments including consumer electronics, displays, safety and defense technology, communication, metrology and sensing among others. Additionally, photonics also finds application across medical and health care, and the high performance computing segment. Medical and healthcare is one of the fastest growing application segments for photonics based instruments. The term photonics developed as an outgrowth of the first practical semiconductor light emitters invented in the early 1960s and optical fibers developed in the 1970s.

Wave guides, optical modulators, optical interconnects, LED, wavelength division multiplexer filters, photo detectors, lasers, amplifiers and spectroscopes among others are the major products of photonics. The prices of photonics based equipment are less compared to conventional devices. Lower power consumption and need for high-speed electronics are the major factors fuelling the demand for photonics. Wavelength division multiplexer filter is one of the major products for photonics. Increasing demand for high speed communication is one of the major factors fueling the demand for wavelength division multiplexers.

(Ref: Quora )

Photonics is closely related to optics, quantum optics, optomechanics, electro-optics, optoelectronics and quantum electronics. Classical optics long preceded the discovery that light is quantized, when Albert Einstein famously explained the photoelectric effect in 1905. Optics tools include the refracting lens, the reflecting mirror, and various optical components and instruments. Key tenets of classical optics, such as Huygens Principle, Maxwell's Equations and the wave equations, do not depend on quantum properties of light. However, each area has slightly different connotations by scientific and government communities and in the marketplace. Quantum optics often connotes fundamental research, whereas photonics is used to connote applied research and development.

Photonics also relates to the emerging science of quantum information, in those cases where it employs photonic methods. Other emerging fields  include opto-atomics, in which devices integrate both photonic and  atomic devices for applications such as precision timekeeping,  navigation, and metrology; polaritonics, which differs from photonics in that the fundamental information carrier is a polariton, which is a mixture of photons and phonons, and operates in the range of frequencies from 300 gigahertz to approximately 10 terahertz.

(Ref: Shashank Rai )