Since the beginning of the Covid-19 pandemic, washing hands has become as common as leaving the footwears at the doorstep. But have you ever wondered why the color of the foam produced is white irrespective of the color of the soap? There are two main reasons. Firstly, the colorants that are added in the soap are of small proportion, as large proportion of it would stain the hands. The second reason seems quite interesting. The foam is formed due to the combined effect of soap liquid, air and water. The surface tension is responsible for obtaining the shape of the bubble. The bubble is completely transparent and acts as a mirror reflecting the light that is present in the surrounding. Since most of the light in the surrounding is white light, the phenomena of scattering of light comes into play and we tend to see white foam. So, we see the foam to be red in color when we expose the foam to red light.
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Essay on the works of KS Krishnan
Introduction:
“Science is not only a disciple of reason but, also, one of romance and passion” – Stephen Hawking. This very statement can be read as a statement by any educated soul but can be soul-felt only by fortunate people. And Dr. KS Krishnan (Dr.Kariamanikkam Srinivasa Krishnan) is one among them. His contributions to physics are in diverse fields. He has taken the role of a research scholar, reader of physics, professor, head of the department and so on in his career. He always told his students, “Physics means facing facts”.
Collaboration with Dr. CV Raman:
Dr. KS Krishnan was promptly given a research assistantship by Dr. CV Raman when he attended classes at the University College of Science. The laboratories in the University College of Science were just being set up and were not fully equipped at that time. Because of this, the students of the college had to often brainstorm and set up experiments on their own. This conferred them initial exposure to the experimental Physics and helped them to develop appreciable skill set of working with hand creating an excellent ambience for learning physics. This became a great advantage to Dr. KS Krishnan. He learned the different branches of Physics thoroughly before becoming a member of Raman’s research team. He trained himself in mathematics, seeking help from the Mathematics Faculty at the University. In November 1923, Dr. KS Krishnan officially joined Indian Association for the cultivation for science (IACS) as a research scholar to work under Raman’s supervision. Afterwards, he spent five years at the Association under the close guidance of Raman.
He started investigating the scattering properties of 65 dust-free liquids and its theoretical interpretations. He conducted extensive experiments in the summer of 1924 and concluded that a feeble fluorescence was evinced by several liquids and that the selected blue region of the incident white light beams excited fluorescence in the green. His first scientific paper with the above-mentioned results was published in 1925 in Philosophical Magazine under the title “On the molecular scattering of light in liquids”. Raman was deeply impressed by his sovereign, creative and authentic research capabilities.
The Raman effect:
It was during 1926 and 1927 that Dr. KS Krishnan’s collaboration with Dr. CV Raman really blossomed. The problems they worked on during this time included classical optics, electro- and magneto-optics, light scattering in fluids, flow birefringence, the Maxwell effect in liquids, etc. Dr. CV Raman’s administrative and teaching engagements made it difficult for him to dedicate time in his laboratory at the Association. In such moments, Dr. KS Krishnan undertook the natural role of leader. He also worked as an associate with Dr. CV Raman and together they published in Nature, “Optical analogue of the Compton effect” on May 5,1928. They assumed the X-ray scattering of the ‘unmodified’ type observed by Prof. Compton corresponding to the normal or average state of the atoms and molecules, while the ‘modified’ scattering of altered wave-length corresponding to their fluctuations from that state. From which they expected the same in the case of ordinary light which yields two types of scattering, one determined by the normal optical properties of the atoms or molecules, and another representing the effect of their fluctuations from their normal state. Through experiments they also confirmed that in every case in which light is scattered by the molecules in dust-free liquids or gases, the diffused radiation of the ordinary kind, having the same wave-length as the incident beam, which is accompanied by a modified scattered radiation of degraded frequency.
He was one among the thirteen scholars who worked with Dr. CV Raman at the time of discovery of Raman effect and played a significant role in it. When a controversy aroused on who deserves the Nobel prize for the Raman effect, Dr. KS Krishnan humbly called it a blatant misinterpretation. In the time and space, where people fought to claim their recognition for their contributions, Dr. KS Krishnan remained as a ‘Man of simplicity’. He never expressed his sense of disappointment at being left out, no matter what his inner feelings were. His relationship with Raman remained as cordial as before. However, in one of the written testimonials, Dr C V Raman shows how important the contribution of Dr. KS Krishnan was in getting the Noble Laureate.
On 4th October 1928, Professor Arnold Sommerfeld arrived in Calcutta gave seven lectures on “Modern developments in wave mechanics”, of which Dr. KS Krishnan took down notes. He independently worked on the intermediate mathematical steps for making the lectures clear and coherent. Sommerfeld was impressed by his ingenuity and scholarship and applauded his classic mathematical proofs.
Research at Dhaka University:
By 1931, Dr. KS Krishnan was recruited to Dhaka where he turned his attention to study the physics behind the para and diamagnetism. He developed exquisite and precise experimental techniques to measure the magnetic anisotropy of dia- and paramagnetic crystals. He was able to correlate the anisotropy of crystals with the anisotropy and arrangement of individual molecules or ionic groups. He along with his students were able to determine the orientation of molecules in the unit cell from magne-crystallic measurements. His research team developed methods for the accurate measurement of feeble susceptibilities and anisotropies. He invented a method based on the instability of the crystal when the crystal is twisted too far from the orientation, in which its strongest principal axis lies along the field. In this period, his research group published papers in renowned international and national journals. His papers on magne-crystallic phenomenon brought him appreciation all around the world. He built a research school on crystal magnetism in Dhaka, and his students were his main collaborators. In 1931, He was approved a permanent position in Dhaka University. In 1933, he submitted his doctoral dissertation to the Madras University; the thesis titled “Magnetic susceptibilities of crystals in relation to crystal structure” was submitted supplicating for the DSc degree. His examiners were impressed with his doctoral research and Nobel Laureate Physicist W. H. Bragg wrote a review on the same.
Research at IASC Calcutta:
After receiving the DSc degree, IACS in Calcutta offered him the post of the Mahendra Lal Sircar (MLS) Research Professorship.He joined IACS as the first MLS Professor on 21st December 1933. He moved to Calcutta, where he had the opportunity of working with Dr S.N. Bose. Dr S N Bose called it a good experience working with him and his students. He also collaborated with Dr. Santilal Banerjee to elaborate on the magnetic properties of crystals in relation to their structure. Their joint papers and communications (published in Nature, Terrestrial Magnetism and Atmospheric Electricity, and by the Royal Society), remain to this day, aside from a number of other pathbreaking contributions they also published in various Physics journals, the most definitive scientific studies on the structure and tendencies of small crystals. Their experiments in Dhaka and continued collaborative research in Kolkata led to what is now known as the Krishnan Banerjee method in measuring the magnetic susceptibility of small crystals.
International recognition to Dr. KS Krishnan’s work:
Dr. KS Krishnan’s works on paramagnetism in salts and diamagnetism in graphite brought him many international connections. He, along with other rising scientists such as Santilal (S.) Banerjee, B.C. Guha, and Asutosh Mookerjie developed an elegant and precise experimental technique to measure the magnetic anisotropy of diamagnetic and paramagnetic crystals. Their findings were published by the Royal Society of London in 1933 under the title, Investigations on Magne-Crystallic Action. He was invited by Lord Rutherford to the Cavendish Laboratory, Cambridge, and by Sir William Bragg to the Royal Institution, London, to deliver courses of the lecture. In Cambridge, his initial two lectures were on diamagnetism and paramagnetism in crystals. The third lecture was about absorption and fluorescent spectra of certain aromatic compounds. After delivering lectures in Cambridge, he moved to London to deliver three public lectures at the Royal Institution. The title of his talk was “Some aspects of crystal Physics”. His work on the anisotropic susceptibility of graphite provided the concrete evidence of the validity of the quantum-mechanically based electron theory of metals. His work on graphite laid the founding stone for the field of the electronic structure of graphite. Dr. C V Raman being a fellow of the Royal society nominated Dr. KS Krishnan and in the year 1940, he was elected as ‘The Fellow of the Royal Society’ which is great honour for every scientist.
Research at Allahabad university:
His popularity grew in India after receiving the acclamation from scientific community in the west. Later joined the professorship at Allahabad University at the request of the famous palaeobotanist Prof. Birbal Sahni, where he took up the physics of solids, in particular of metals. He arrived at Allahabad University in 1942. He was an excellent teacher and taught subjects with passion. Because of his finest notoriety in teaching and research, Allahabad University started drawing bright young students. During his tenure at Allahabad University, he wrote two research papers on pure mathematical problems. The first paper titled “A Simple Result in Quadrature” was published in Nature. It dealt with the summation of certain infinite series with special properties. The second paper titled “On the equivalence of certain infinite series and the corresponding integral” was published inthe Journal of Indian Mathematical Society.
The other areas of reaseach:
In 1960, Ziman published his erudite work on the electrical properties of liquid metals and in his review, he acknowledged the inaugural work done by Bhatia and Dr. KS Krishnan. The theory of the electrical resistivity of liquid metals is now called the Bhatia-Krishnan-Ziman Theory. He was in very core group of scientists along with Homi Bhabha and S. S. Bhatnagar. In 1947, Jawaharlal Nehru requested him to assist him in Delhi as a scientific administrator. He took the charge as the first director of the National Physical Laboratory (NPL) in Delhi. While working in Delhi, he identified two new areas of research: Lattice oscillations in ionic crystals and thermionic properties of metals and semiconductors. Realizing the time crunch, he took a new PhD student S. C. Jain and appointed one of his students S. K. Roy as a Teaching Assistant at NPL. With Roy, Dr. KS Krishnan published papers on lattice dynamics and polarization fields in crystals whereas with Jain, he co-authored research papers on thermionics.
Dr. KS Krishnan as a person
He was very polite, humorous, witty and composed person. Through his sheer hard work, he won significant awards and honors. He was knighted in the 1946 Birthday Honours List and awarded the Padma Bhushan by the Government of India in 1954. He was the first recipient of the prestigious Bhatnagar Award in 1958. He was also a fellow of numerous national and international scientific academies. He was also a philosopher and a great scholar of Tamil and Sanskrit. He was fascinated by the biographies of famous scientists like Lord Kelvin, Hermann von Helmholtz, Lord Rayleigh, J. C. Maxwell and Peter Tait. The scientific writings of Lord Rayleigh, Albert Einstein and Niels Bohr had a philosophical influence on his life. During his early college days in Madras. He was inspired by Srinivasa Ramanujan, Dr. CV Raman and had a great admiration for Dr.S. N. Bose as a giant theoretical physicist.
Conclusion:
In his research career, Dr. KS Krishnan published 135 papers out of which 50 papers were in spectroscopy, 60 papers were in magnetism, 23 papers were in thermionics and two papers of ‘Popular’ nature. He embraced his passion for physics till the very moment before his death. His last paper was finalized on the day of his death and came out a month after his death. He definitely is a role model for the current generation to emulate.
Refrences:
https://www.beaninspirer.com/kariamanickam-srinivasa-krishnan-earth-genius-co-discoverer-raman-effect/
We have come across circuit diagrams that has the batteries, resistors and so on. We do mention the direction of flow of current in the circuit with the help of arrow marks. We have also come across Kirchhoff’s first law that states that current flowing into a node (or a junction) must be equal to current flowing out of it. Some of us have may have raised a question of what happens to the current that flows across a resistor. Consider a water tap and a gardening hose water pipe. If the breadth of the pipe is larger, the water flows out easily from a large diameter. If the breadth of the pipe is smaller than the normal size, then the water does flow out but from a small diameter. The point is, the velocity at which the water flows at both the ends of the pipe is the same. Though the velocities are different for different diameters of pipe,the amount of water that enters the pipe, leaves the pipe. If there is a difference in the velocities at then ends, it means that there is either a leak in the pipe or a region in the pipe where the water is stored which leads to bursting of the time after a while. The amount of water is analogous to the amount of charge(current) and the pipe is analogous to the resistor (larger diameter pipe- less resistance; smaller diameter pipe- more resistance). The amount of charge entering the resistor is same as the charge flowing out of the resistor and therefore there is no reduction in the value of current.
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Nanoscience
By definition, Nanoscience is the emerging study of science that deals with the properties of materials that are of size below the billionth of a meter. Why is it important? The very first computer weighed more than 30 tonnes and occupied a size of a room. A recent survey found that more people in the world own a cell phone than own a toothbrush and the credit goes to Nanoscience. “There’s plenty of room at the bottom: An invitation to enter a new field of physics” was a lecture given by physicist Richard Feynman at the annual American Physical Society meeting at Caltech on December 29, 1959, in which Feynman laid the foundation for Nanoscience and Nanotechnology. Nanoscience is an interdisciplinary course that brings in the concepts of physics, chemistry, biology and computer science. Its application extends from daily needs to defense.
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Asteroid Day
Asteroids are rock-like celestial objects in the space that orbit the sun. These minor planets are mainly made up of metals and rocky materials. Majority of asteroids are found in the main asteroid belt (a region between the orbits of Mars and Jupiter).How are they different from planets ? Unlike planets, Asteroids are small in size, irregular in shape and do not follow a perfect elliptical path. Due to the small size, Asteroids experience perturbation ( subject to many forces ) which directs some of them towards the Earth’s atmosphere. Asteroids that has entered into the Earth’s atmosphere are called meteors. Once they enter the Earth’s atmosphere, they gain a large momentum and bring about disastrous impact if their size is beyond 25 meters (otherwise would end up burning in the atmosphere itself) Asteroid Day is observed globally on June 30 in order to “observe each year at the international level the anniversary of the Tunguska impact (the most harmful known asteroid-related event on Earth in recent history ),over Siberia, Russian Federation, on 30 June 1908, and to raise public awareness about the asteroid impact hazard.”Huge Asteroids on explosion can release gases that can block the Sunlight completely and cause nuclear winter which indeed reduces the temperature at which humans cannot survive. The recent studies have proven that the extinction of dinosaurs which was once considered as an impact of volcanic eruption, is actually due to the Asteroid impact. In-fact volcanic eruptions have decreased the impact. Many of the cosmologists, theoretical physicists including Stephen Hawking, have predicted that the doomsday would arise due to Asteroids and researches are being carried out to detect the harmful asteroids and find ways to prevent its massive impact.
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Does the sun rotate?
The answer is YES !. The Sun rotation varies by latitude and it rotates on its own axis once in about 27 days. How was it possible to detect the rotation of a star of surface temperature about 5800 Kelvin and located at the center of the solar system which is about 152.03 million km away from the Earth ? Sun spots. Yes, Sun spots, as the name suggests,are the darker areas on the surface of the sun. Sun spots are areas where the magnetic field is about 2,500 times stronger than Earth’s. Because of the strong magnetic field, the magnetic pressure increases while the surrounding atmospheric pressure decreases. This in turn lowers the temperature relative to its surroundings because the concentrated magnetic field inhibits the flow of hot, new gas from the sun’s interior to the surface thereby appearing darker.The number of sunspots has a cyclical increase and decrease over an approximately 11-year period known as the solar cycle. As these spots are located at the surface, they tend to move along solar disc validating the rotation of the sun on its own axis. Sun spots are not just the characteristic features of the sun. Their impact on Earth is indeed devastating. Increased sun spots correspond to increased solar activity which includes Coronal Mass Ejections(CME),solar flares and so on. These phenomena lead to geomagnetic storms, the increase in the Northern and southern lights and a possible disruption in radio transmissions and power grids.
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How do oscillations occur?
Oscillation is a type of harmonic motion, typically periodic, in one or more dimensions. Elastic property of the material is the most important aspect for a solid to oscillate. However, elasticity is the property of a solid to regain its shape. How can these cause oscillations? Let us consider a spring hanging vertically downward with one end fixed at the wall. The spring is in equilibrium (no external forces acting on it). When we displace the position of the free end of the spring upward (contracting) or downward (stretching), the restoring force comes into play and tends to bring back the spring to its equilibrium position imparting a negative velocity. Inertia on the other hand tries to oppose any change in velocity. When the body reaches the equilibrium position, the negative velocity is maximum producing a negative displacement. The body then overshoots the position of equilibrium. The restoring force is positive (in a direction opposite to the direction of restoring force considered before) and it must now overcome the inertia of negative velocity. The velocity keeps decreasing until it reaches zero but by this time the displacement becomes large and negative where again restoring force comes into play and the tussle ensues. Thus the oscillation of a physical system results from two basic properties elasticity and inertia.
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Peltier effect
The cooling of one junction and the heating of the other when electric current is maintained in a circuit of material consisting of two dissimilar conductors. Peltier effect was discovered in 1834 by the French physicist Jean-Charles Athanase Peltier. The Peltier effect is the reverse phenomenon of the Seebeck effect. Seebeck effect is the conversion of temperature differences directly into electricity. This effect is named after German Physicist Thomas Johann Seebeck. In 1821, Johann Seebeck discovered that a compass needle would be deflected by a closed loop formed by two metals joined in two places, with a temperature difference between the junctions. This was because the metals responded differently to the temperature difference creating a current loop and a magnetic field. In 1834, Peltier found that an electrical current would produce a temperature gradient at the junction of two dissimilar metals when the current direction was reversed, the cold junction would get hot while the hot would get cold. Applying a current (e- carriers) transports heat from the warmer junction to the cooler junction.The Peltier effect can be used to create a refrigerator that is compact and has no circulating fluid or moving parts. Such refrigerators are useful in applications where their advantages outweigh the disadvantage of their very low efficiency. The Peltier effect is also used by many thermal cyclers, laboratory devices used to amplify DNA by the polymerase chain reaction (PCR). PCR requires the cyclic heating and cooling of samples to specified temperatures. The inclusion of many thermocouples in a small space enables many samples to be amplified in parallel.
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How does the refrigerators work?
What happens when we place hot coffee on a table ? As time passes, the temperature of coffee reduces so that it is equal to the surrounding temperature in which it is placed. The same mechanism is applied in refrigerators. The continuous flow of cold substance in refrigerators makes it a ‘surrounding of low temperature’ that it cools the object placed in it. So how to create this continuous flow ? A refrigerant ( Why not any other substance ? Refrigerant is a substance that can easily undergo phase transition) is passed through a compressor and its pressure is increased. As pressure increases, the temperature also raises due to decrease in volume. This superheated high pressure vapour is passed into the condenser coils( the zig zag wires at the back of refrigerators ) which reduces the temperature of the refrigerant to liquid phase. The high pressure liquid is then passed into the throttling device which is a small diameter spiral valve. When the liquid is passed into this small valve, the temperature reduces( the same way as the perfume that comes out of the small opening of a perfume bottle is found to be cooler). The cold liquid is then passed to the evaporator that is located inside the refrigerator. Through evaporator fans, the cooled air caused by the continuous flow of cooled liquid circulated throughout the refrgerator absorbing heat from the objects placed inside. On evaporation, the liquid undergoes phase change to low pressure vapour and is directed to the compressor. The cycle continues…
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What is an MRI?
How about locating a scar in your hand. One can easily detect it by simply by looking at it with the help of one’s own eyes if that person doesnt have any vision related problems. How about locating a scar on one’s face. One needs to look for a mirror or a camera. How about locating a tumor in one’s body. Now one is in need of a special device to look into the body as one just cannot cut open or operate body every time. This special device is MRI (Magnetic Resonance Imaging). As its name suggests it uses magnetic field for imaging. Our body is made up of millions of atoms. These are in constant random motion. Especially there are a large number of water molecules which contain hydrogen that possess high magnetic moment, meaning it can align itself in presence of magnetic field. So, using magnetic field one can align the protons in one direction. When additional energy in the form of a radio wave is given, the magnetic vector gets deflected causing the hydrogen nuclei to resonate. Different slices of the body resonates with different frequencies. When the radio wave is turned off, the magnetic vector returns to the resting state and causes a signal to be emitted. These signals are used to create the MR images. In a nutshell, the mechanism of MRIs are more like a carbon copy paper where the force applied by the pen is the radiowave.