A BRIEF OVERVIEW OF THE PREVIOUS CLASS AND UPSC PAPER DISCUSSION (05:06 PM)

CONTRIBUTIONS OF INDIANS IN SCIENCE AND TECHNOLOGY (05:10 PM)

• Dr. C V Raman 
• He is known for an effect named after him i.e. Raman effect
• Raman effect is the inelastic scattering of photons after interaction with a molecular sample thus the frequency of scattered light can increase or decrease compared to the original frequency.
• Raman effect has applications in spectroscopy with the help of laser light which is called "Laser Raman spectroscopy"
• Spectroscopy
• It involves analyzing detailed patterns of light that materials emit, absorbs, transmit, or reflect. 
• Different materials interact with different wavelengths in different ways which depends upon material composition and temperature. 
• Examples- Water inside the microwave oven boils very fast whereas the ceramic bowl does not get affected.
• Glass is opaque for the infrared and transparent to visible light. 
• Universe is expanding and this can be proved because of the Redshift phenomenon, which means the original light's wavelength has increased as it is moving farther. 
• Blue light is scattered most by the atmosphere which is why the sky appears blue. 
• Raman spectroscopy 
• Raman spectroscopy is a powerful technique because of various reasons 
• a) It is non-destructive in nature 
• b) It can provide information easily and quickly 
• c) It is sensitive to small changes in material structure. 
• d) It can work on a very small sample
• e) It is used to analyze living cells and tissues along with applications in various industries such as chemicals, Pharma, and electronics among others. 
• 
• Dr Raman was awarded Nobel Prize for physics in 1930, and Bharat Ratna in 1954, and India celebrates National science day on 28th February to commemorate the discovery of the Raman effect. 
• Properties of Laser light 
• Intensity is higher and Directional [Intensity= Energy per unit area per second] [* Normal light expands when covers a distance but the Laser light remains directional]. 
• The laser can cut through Metal.
• Monochromaticity- Light of one frequency and one wavelength. 

DR. SUBRAMANIUM CHANDRESEKHAR (05:43 PM)

• Dr Chandresekhar was an Indian American Astrophysicist who was awarded a 1983 Nobel Prize for Physics for his theoretical studies regarding the structure and evolution of stars.
• He worked on theoretical models of the later evolutionary stages of massive stars
• Stellar cycle 
• 
• A Young star is formed in a region known as Nebulae which has all the required raw material for stars to form. Stars remained brightened because of the Fusion of Hydrogen in Helium as the Hydrogen gets exhausted it becomes a Red Giant where the outer layer expands and the inner layer collapses. This can lead to more nuclear fusion of helium nuclei leading to a White Dwarf star. 
• 
• Dr. Chandrasekhar hypothesized that in high-mass stars the core undergoes violent collapse leading to a powerful explosion known as Supernova
• Depending on the mass of collapsing core it can result in a Neutron star or a Black hole. A neutron star often spins very fast on its axis producing powerful beams of energy which are called Pulsar
• Magnetars are very large neutron stars. 
• The black hole is a region where the escape velocity becomes more than the speed of light hence even light can not escape. 
• For a Supernova explosion to occur, Dr Chandresekhar gave a limit known as the Chandrasekhar limit (More than 1.4 times the Mass of the Sun)
• 

PROJECT EVENT HORIZON TELESCOPE (06:43 PM)

• The Event Horizon Telescope is an international collaboration capturing images of black holes using a virtual Earth-sized telescope.
• A lot of particles swirling around the centre can be imaged
• 

DR. SATYENDRA NATH BOSE (06:48 PM)

• Dr Bose was a theoretical physicist known for his work on a class of particles named after him i.e. Bosons. He used quantum mechanical techniques to explain how a group of Identical photons will behave. He sent this paper to Einstein who got it published in a research journal. This led to the development of Bose-Einstein statistics. Any particle that follows this rule is called Bosons. 
• Einstein generalized the idea propounded by Bose and extended it to atoms. This led to the prediction of a new state of matter (* 5th State) known as Bose-Einstein condensate). It exists at very low temperatures i.e. close to absolute zero (-273.15 degrees celcius) where most of the atoms occupy a single state. 
• Bose-Einstein condensate (BECs) exhibit some amazing phenomena such as Superconductivity, Superfluidity, and the speed of light reduces significantly in BECs. 
• Superconductivity 
• Superconductivity is a phenomenon where resistance becomes Zero thus we can store and transport energy with zero loss. 
• Superconductors do not allow a magnetic field to exist inside them. This has many applications, the most important being magnetic levitation or MagLev. 

BASIC IDEAS ABOUT PARTICLE PHYSICS (07:20 PM)

• The most famous theory in particle physics is the standard model. It is a theory of fundamental particles and how they interact.  
• 
• The basic building block of the universe comprises of
• 6 Leptons- Electrons, Muons, Tau, Electron Neutrino, Muon Neutrino, and Tau Neutrino
• And 6 quarks-  Up, Down, Charm, Strange, Top, Bottom. 
• These fundamental particles interact via three fundamental interactions 
• a) Electromagnetic interaction
• b) Strong interaction 
• c) Weak interaction 
• Mediated by Bosons
• The standard model does not account for gravitational interaction

• Fundamental Interactions	Gravitational interaction	Electromagnetic	Strong	Weak
  Particles affected	Mass	Charged	Quarks	Quarks and Leptons
  Mediating particles	Graviton	Photons	Gluons	W and Z bosons
  Range	Long range	Long range	Short range	Short range
  Relative strength	Weakest (4)	(2)	Most powerful (1)	(3)
  Role	Planets, stars, Galaxies	Atomic molecules	Nuclear stability	β-decay reaction inside stars

INDIAN NEUTRINO OBSERVATORY (07:53 PM)

• [* Positron- it is the anti-particle of the electron. Every fundamental particle has its anti-particle] 
• 
• When these anti-particles combine together then they can form Anti-matter. 
• Neutrinos
• These are elementary particles belonging to the Lepton family. There are three neutrinos with zero charge and extremely low mass, and they only interact through weak interaction and gravity. 
• Neutrinos keep changing into each other as they travel. This is called Neutrino oscillation. They are the second most abundant particle in the universe. For example- Billions of Neutrinos cross us every second without any interactions. 
• Indian neutrino observatory is an under-construction research facility in Bodi Hills, Theni district, Tamilnadu. It will use an Iron calorimeter to detect both natural and artificial neutrinos. 
• [* Recently Muon was in the news, as Earth receives a lot of cosmic radiation from distant stars and galaxies. These Muons penetrate through solid particles. This can be used to know the interiors of the solid structure. Muon tomography was used to know the presence of rooms inside the great pyramids.
• How many Muons are falling and how many are recorded, this pattern can be recorded by the computer and the inside structure can be known] 

The topic for the next class- Continuation of Particle Physics.