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Bikramjit radiation physics lecture1
- 1. Radiation physics Lecture 1 Disclaimer::Images are subject to copyright and not used for commercial purpose.
- 2. Radiation physics Lecture 1 Bikramjit Chakrabarti, MD, DNB • Structure of atoms • Production of X-rays • Nuclear transformations
- 3. ENGLAND: Rutherford DENMARK: Niels Bohr FRANCE: Curie GERMANY: Einstein ITALY: Fermi GERMANY: Planck
- 4. A brief history of discovery of atomic structure • Discovery of cathode ray, X-ray • Discovery of radioactive elements – natural and artificial, • Discovery of nucleus, atomic and fundamental particles.
- 5. John Dalton (1803) 1. All elements are composed of atoms, which are indivisible and indestructible particles. 2. All atoms of the same element are exactly alike; in particular, they all have the same mass. 3. All atoms of different elements are different; in particular, they have different masses. 4. Compounds are formed by the joining of atoms of two or more elements. In any compound atoms combined only in small whole-number ratios, such as 1:1, 1:2, 2:1, 2:3, to form compounds.
- 6. Cathode Ray - Johann Hittorf & Eugen Goldstein (1869) Cathode ray causing fluorescence on glass wall. Shadow of fan is deviated when magnetic field is applied.
- 7. Cathode ray •Traveled in a straight line •Their path could be "bent" by the influence of magnetic or electrical fields •A metal plate in the path of the "cathode rays" acquired a negative charge •Produce fluorescence
- 8. Wilhelm Roentgen (1895) New type of ray that 1.Could pass unimpeded through many objects 2.Were unaffected by magnetic or electric fields 3.Produced an image on photographic plates (i.e. they interacted with silver emulsions like visible light) 4.Produced fluorescence 5.Ionized a gas
- 9. X ray production Vacuum glass tube Vacuum glass tube Cathode made of tungsten filament Cathode made of tungsten filament High voltage (10V, 6A) for TI E High voltage (10V, 6A) for TI E Thick copper rod Thick copper rod High Z, High melting point High Z, High melting point Cu: absorbs stray electrons, W: absorbs stray XR Cu: absorbs stray electrons, W: absorbs stray XR Coolidge tube
- 10. • Focal spot: Line focus (a sinѲ) • Heel effect • Circuitry: step-up transformer and rheostat • Tube voltage measured by sphere gap method. • Efficiency= OE/IE, • Output = exposure = ionization produced, depends on voltage.
- 11. • The probability of bremsstrahlung emission is proportional to the value of Z2 • Fluorescent yield: Probability to produce characteristic X-rays. • Typical anode currents, depending on the examination mode, are <10 mA in fluoroscopy and 100 mA to >1000 mA in single exposures. • The typical range of tube voltages is 40–150 kV for general diagnostic radiology and 25–40 kV in mammography.
- 12. Properties of X-ray produced Heterogeneous: The energy of the Bremsstrahlung photon depends on • the attractive Coulomb forces and hence on the distance of the electron from the nucleus. • Energy of incident electrons Self-filtration: X rays are not generated at the surface but within the target, resulting in an attenuation of the X ray beam. This self- filtration appears most prominent at the low energy end of the spectrum. Additionally, characteristic radiation shows up if the kinetic electron energy exceeds the binding energies. L radiation is totally absorbed by a typical filtration of 2.5 mm Al. For tungsten targets, the fraction of K radiation contributing to the total energy fluence is less than 10% for a 150 kV tube voltage.
- 13. Contd.. • For mammography, other anode materials such as molybdenum (Z = 42) and rhodium (Z = 45) are frequently used. For such anodes, X ray spectra show less contribution by bremsstrahlung but rather dominant characteristic X rays of the anode materials. This allows a more satisfactory optimization of image quality and patient dose. In digital mammography, these advantages are less significant and some manufacturers prefer tungsten anodes. • Off focus radiation: Extrafocal radiation can contribute up to ~10% of the primary X ray intensity. Sometimes, parts of the body are imaged outside the collimated beam by off focus radiation. Off focus radiation also increases patient dose. The best position for a diaphragm to reduce off focus radiation is close to the focus.
- 14. Antonio Henri Becquerel (1896) Radioactivity – radiation from nucleus Photographic plate with potassium uranyl sulfate crystals showed a dark spot even when stored in dark.
- 15. JJ THOMSON (1897) – CRT experiment: Discovery of electron • Electron was discovered by J. J. Thomson in 1897 when he was studying the properties of cathode ray. • J. J. Thomson measured the charge-by- mass-ratio (e/m) of cathode ray particle using deflection in both electric and magnetic field. • em=−1.76×108em=−1.76×108 coul omb per gram • Thompson determined the charge to mass ratio for the electron, but was not able to determine the mass of the electron.
- 16. Marie Sklodowska Curie & Pierre Curie(1898) discovered radium
- 17. In 1899, Rutherford had discovered alpha and beta "rays" from uranium. Now, today we know they are not rays, they are particles; alpha is a nucleus of helium and beta is an electron. Ernest Rutherford (1899)
- 18. Albert Einstein (1905) Nobel prize for work on photo-electric effect !! • The laws of physics are the same for all observers in uniform motion relative to one another (principle of relativity), • The speed of light in a vacuum is the same for all observers, regardless of their relative motion or of the motion of the source of the light. • E= mc2. The faster an object moves, the more massive it becomes. That means that, in theory, no object can ever reach 100 percent of the speed of light because its mass would become infinite. • The general theory of relativity (1916): acceleration distorts the shape of time and space.
- 19. Ernest Rutherford (1908) But why electrons do not radiate energy to spiral into the nucleus? Line spectra not explained
- 20. Ernest Rutherford (1908) 1. Almost all the incident alpha particles go straight and are scarcely scattered. 2. Only occasionally such a large- angle scattering through an angle greater than 90 degrees or near 180 degrees occurs. 3. The scattering rate depends on the atomic weight of the target; the more the atomic weight, the larger the probability.
- 21. Concept of proton (in anode or canal rays) – Goldstein (1908) • The lightest ones, formed when there was some hydrogen g as in the tube, were calculated to be about 1840 times as massive as an electron.Cathode: Perforated, Potential difference: several thousands.
- 22. Niels Bohr (1913) - postulates • Electrons can exist only in orbits where angular momentum = multiple of Planck constant/2π • No energy is gained or lost when in this permissible orbits. • Radiation is absorbed or emitted when an electron moves from one orbit to another. And the energy change E = E2 – E1
- 23. Niels Bohr (1913) – failed to explain • Incorrect value for the ground state orbital angular momentum. • Dual nature of electron and the Heisenberg Uncertainty Principle because it considers electrons to have both a known radius and orbit. • No explanation of fine structure of spectra -Existence of additional quantum numbers. • Poor predictions regarding the spectra of larger atoms. • Does not explain fine structure and hyperfine structure in spectral lines. • No explanation for Zeeman Effect and Stark Effect.
- 24. Arnold Somerfield • He introduced the 2nd quantum number (azimuthal quantum number) and the 4th quantum number (spin quantum number). He also introduced the fine-structure constant and pioneered X-ray wave theory. • Elliptical orbit • Sub-shell s,p,d,f • Modification of angular momentum as given by Bohr.
- 25. Max Karl Ernst Ludwig Plank (1918) • Worked on thermodynamics. • Energy did not flow in a steady continuum, but was delivered in discrete packets Planck later called quanta. • Planck's constant (the proportion of light's energy to its wave frequency, or approximately h = 6.626 x 10-34 J-sec).
- 29. ‘GOD PARTICLES’ ARE BOSONS The “God particle” nickname actually arose when the book The God Particle: If the Universe Is the Answer, What Is the Question? by Leon Lederman was published.
- 30. • In 1924, Satyendra Nath Bose published an article titled Max Planck's Law and Light Quantum Hypothesis. This article was sent to Albert Einstein. Einstein appreciated it so much that he himself translated it into German and sent it for publication to a famous periodical in Germany - 'Zeitschrift fur Physik'. The hypothesis received a great attention and was highly appreciated by the scientists. It became famous to the scientists as 'Bose-Einstein Theory‘. • A Bose–Einstein condensate (BEC) is a state of matter of a dilute gas of bosons cooled to temperatures very close to absolute zero (that is, very near 0 K or −273.15 °C). Under such conditions, a large fraction of bosons occupy the lowest quantum state, at which point macroscopic quantum phenomena become apparent.
- 31. 89 years later.... • The Nobel Prize in Physics 2013 was awarded jointly to François Englert and Peter W. Higgs "for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN's Large Hadron Collider. And now boson became ‘Higgs Boson’ !!!!!
- 32. Louis de Broglie (1925) – Wave-particle duality • Wave like properties: eg refraction, • Particle like properties: eg momentum • Uncertainty about position and momentum of wave. • E= hv = hc/λ
- 33. Erwin Schrödinger (1926) -quantum mechanical model of the atom. • By solving the Schrödinger equation (Hψ = E ψ), we obtain a set of mathematical equations, called wave functions (ψ), which describe the probability of finding electrons at certain energy levels within an atom..
- 34. Quantum number of electrons QUANTUM NUMBERS OF ELECTRON VALUE SPECIFIES Principal Quantum Number (n) n = 1, 2, 3, …, ∞ Energy of an electron and the size of the orbital Angular Momentum (Secondary, Azimunthal) Quantum Number (l) l = 0, ..., n-1. Divides the shells into subshells (s,p,d,f) Magnetic Quantum Number (ml) ml = -l, ..., 0, ..., +l. divides the subshell into individual orbitals Spin Quantum Number (ms) ms = +½ or -½. Specifies the orientation of the spin axis of an electron. • Atomic orbital describes a region of space in which there is a high probability of finding the electron. Energy changes within an atom are the result of an electron changing from a wave pattern with one energy to a wave pattern with a different energy (usually accompanied by the absorption or emission of a photon of light). • Each electron in an atom is described by four different quantum numbers. The first three (n, l, ml) specify the particular orbital of interest, and the fourth (ms) specifies how many electrons can occupy that orbital.
- 35. James Chadwick (1935) Discovery of neutron Schematic diagram for the experiment that led to the discovery of neutrons by Chadwick. 4Be9 +2α4 [⟶ 6C13 ] [⟶ 6C12 ]+0n1
- 36. Wolfgang Pauli (1945) Pauli exclusion principle, a quantum mechanical principle No two electrons in the same atom can have identical values for all four of their quantum numbers. Two electrons in the same orbital must have opposite spins.
- 37. Enrico fermi • Built first nuclear reactor • Postulated and named neutrino, • Described weak nuclear force, • He was present at the Trinity test on 16 July 1945, where he used his Fermi method to estimate the bomb's yield. • Fermions are named after him.
- 39. Commonly used γ-emitters ISOTOPE SOURCE HALF LIFE PRODUCT ENERGY HVL Pb 88Ra226 NATURAL 1622 yrs 82Pb206 0.83 MeV 16-20 mm 27Co60 27Co59 5.26 yrs 28Ni60 1.25 MeV 11 mm 55Cs137 92U235 30 yrs 56Ba137 0.66 MeV 6.5 mm 77Ir192 77Ir191 74 days 78Pt192 0.38 MeV 6 mm 46Pd103 46Pd102 17 days 45Rh103 0.021 MeV 53I125 54Xe124 60 days 52Te125 0.026 MeV 0.025 mm 53I131 52Te130 8 days 54Xe131 0.364 MeV 43Tc99m 42Mo98 6 hrs Tc99 0.14 MeV PURE BETA EMITTERS ALPHA EMITTERS NEUTRON EMITTER POSITRON EMITTER Y90 , Sr90 , P32 , Tl204 , C14 , tritium (H3 ) Bi212 , Pb212 , Ac225, Po210 , U238 Cf252 F18 , C11 , O15 , N13
- 40. • Difference between molecule, atom, radical, ion • Size of atom: 10-10 m, nucleus: 10-15 m. • Nucleus • Atomic mass: Amu = 1 /12 of C12 = 1.66 X 10-27 kg = 931.5 MeV (1 eV = 1.602 X 10-19 J) • No of atoms per gram = NA/AW • No of electrons per gram = NA*Z/AW • Energy levels of – Atoms – Nucleus: Mass defect = binding energy of nucleus Alpha particle requires nearly 30 Mev to cross potential barrier of nucleus. – Electron: Potential energy = negative of binding energy.
- 41. Electron • Unit negative charge: 1.602X 10-19 C • Mass: 5.48 X 10-4 amu • K,L,M shells: 2n2 • Proton: • Mass: 1.00727 amu
- 42. Identify… • Atomic number • Mass number • Isobar • Isotope • Isotone • Isomer • Radio-isotope vs radio-nuclide
- 43. Fundamental particles FERMION BOSON Matter particles 12 in number Types: 6 quarks + 6 leptons Odd half-integer spin of quantum units of ang mom. Messenger particles 13 in number Types: Photon, gluon, Weak force, gluon, gravitron etc. Integer spin (0,1,2)
- 45. Nuclear stability Becomes stable by nuclear conversion • n/p ratio (N:Z ratio):1 • Even-even nuclei (n,p mutually paired) • The magic numbers are: – proton: 2, 8, 20, 28, 50, 82, 114 – neutron: 2, 8, 20, 28, 50, 82, 126, 184
- 46. Alpha decay 2 neutrons + 2 protons ejected as helium nucleus • Most common type of decay, • Seen in Z > 82 • Alpha particles are helium nuclei, • Alpha particles have a typical kinetic energy of 5 MeV.
- 47. High n/p ratio - β- decay Neutron converts into proton along with beta ray emission •Beta particles are emitted with a spectra of energy, from zero to a maximum value. •Average energy is 1/3 of maximum energy.
- 48. Low n/p ratio Proton converts into neutron Orbital electron capture (K capture) With characteristic X-ray emission (internal PE effect) β+ decay With positron emission
- 49. Other processes • Internal conversion: – Excess energy liberated as γ → ejects orbital electron → ‘hole’ → characteristic x-ray produced. • Isomeric transition – 99m Tc → 99 Tc
- 50. Transient eq = TcSecular eq = Ra α β Radio-active series Uranium series: U238 → Pb206 Actinium series: U235 → Pb207 Thorium series: Th232 → Pb208
- 51. Nuclear reactions • α-p reaction • α-n reaction • Proton (p,γ; p,n; p,d; p,α reactions): • Neutron bombardment (fast neutrons required if mass difference is high): – n-γ reaction (common) – n-α reaction – n-p reaction • Deuteron (fast neutron stripped): • Photo-disintegration • Fission: High Z → low Z • Fusion: Low Z → high Z
- 52. Remember.. • Activity = number of disintegrations per second. • Decay constant • Half life • Mean or average life = avg time before a particle decays. • 1 Ci = rate of decay of 1 gram radium = 3.7 X 1010 Bq • 1 Bq = 1 dps
- 53. Activating nuclide in nuclear reactor • Chain reaction of fission -> Neutrons generated -> bombarded to produce radio- nuclide from non-radioactive nuclide.
- 54. Lecture 2 Next day • Types of radiation. • Interaction of radiation with matter.
Editor's Notes
- Particle physics is the study of the basic elements of matter and the forcesacting among them. It aims to determine the fundamental laws that control themake-up of matter and the physical universe. Quantum mechanics (QM -- also known asquantum physics, or quantum theory) is a branch of physics which deals with physical phenomena at nanoscopic scales where the action is on the order of the Planck constant. It departs from classical mechanics primarily at the quantum realm of atomic and subatomic length scales
- Particle physics is the study of the basic elements of matter and the forcesacting among them. It aims to determine the fundamental laws that control themake-up of matter and the physical universe. Quantum mechanics (QM -- also known asquantum physics, or quantum theory) is a branch of physics which deals with physical phenomena at nanoscopic scales where the action is on the order of the Planck constant. It departs from classical mechanics primarily at the quantum realm of atomic and subatomic length scales
- 1803 Dalton - the atom is a indivisible, indestructible, tiny ball atom meaning &quot;indivisible&quot; in Greek
- They were first observed in 1869 by German physicist Johann Hittorf, and were named in 1876 by Eugen Goldstein Kathodenstrahlen, or cathode rays.
- Cathode rays and electrons Electrical discharge through partially evacuated tubes produced radiation. This radiation originated from the negative electrode, known as the cathode (thus, these rays were termed cathode rays). The &quot;rays&quot; traveled towards, or were attracted to the positive electrode (anode) Not directly visible but could be detected by their ability to cause other materials to glow, or fluoresce Traveled in a straight line Their path could be &quot;bent&quot; by the influence of magnetic or electrical fields A metal plate in the path of the &quot;cathode rays&quot; aquired a negative charge The &quot;cathode rays&quot; produced by cathodes of different materials appeared to have the same properties
- Henri Becquerel (1896) was studying materials which would emit light after being exposed to sunlight (i.e. phosphorescent materials). The discovery by Roentgen made Becquerel wonder if the phosphorescent materials might also emit x- rays. He discovered that uranium containing minerals produced x-ray radiation (i.e. high energy photons).
- The electron is a subatomic particle, symbol e− or β−, with a negative elementary electric charge.[8]Electrons belong to the first generation of the leptonparticle family,[9] and are generally thought to beelementary particles because they have no known components or substructure.[1] The electron has amass that is approximately 1/1836 that of theproton.[10] Quantum mechanical properties of the electron include an intrinsic angular momentum (spin) of a half-integer value in units of ħ, which means that it is a fermion. Being fermions, no two electrons can occupy the same quantum state, in accordance with the Pauli exclusion principle.[9] Like all matter, electrons have properties of both particles and waves, and so can collide with other particles and can bediffracted like light. The wave properties of electronsare easier to observe with experiments than those of other particles like neutrons and protons because electrons have a lower mass and hence a higher De Broglie wavelength for typical energies.
- Radium was discovered by Marie Sklodowska-Curie and her husband Pierre Curie on 21 December 1898, in a uraninitesample.[14] While studying the mineral earlier, the Curies removed uranium from it and found that the remaining material was still radioactive.
- Einstein worked in a patent office in Bern, Switzerland, from 1902 through 1909 (during the time he published his landmark works). Even people who will be famous have day jobs. He won the Nobel Prize for Physics in 1921. What for? His work on the photoelectric effect, which held that light be considered as consisting of particles called photons.
- Rutherford&apos;s find came from a very strange experience. Everyone at that time imagined the atom as a &quot;plum pudding.&quot; That is, it was roughly the same consistency throughout, with negatively-charged electrons scattered about in it like raisins in a pudding. As part of an experiment with x-rays in 1909, Rutherford was shooting a beam of alpha particles (or alpha rays, emitted by the radioactive element radium) at a sheet of gold foil only 1/3000 of an inch thick, and tracing the particles&apos; paths. Most of the particles went right through the foil, which would be expected if the atoms in the gold were like a plum pudding. But every now and then, a particle bounced back as though it had hit something solid. After tracing many particles and examining the patterns, Rutherford deduced that the atom must have nearly all its mass, and positive charge, in a central nucleus about 10,000 times smaller than the atom itself. All of the negative charge was held in the electrons, which must orbit the dense nucleus like planets around the sun. Ernest Rutherford studied alpha rays, beta rays and gamma rays, emitted by certain radioactive substances. He noticed that each behaved differently in response to an electric field:The b-rays were attracted to the anode The a-rays were attracted to the cathode The g-rays were not affected by the electric field The a and b &quot;rays&quot; were composed of (charged) particles and the g-&quot;ray&quot; was high energy radiation (photons) similar to x-rays b-particles are high speed electrons (charge = -1) a-particles are the positively charged core of the helium atom (charge = +2)
- Rutherford&apos;s find came from a very strange experience. Everyone at that time imagined the atom as a &quot;plum pudding.&quot; That is, it was roughly the same consistency throughout, with negatively-charged electrons scattered about in it like raisins in a pudding. As part of an experiment with x-rays in 1909, Rutherford was shooting a beam of alpha particles (or alpha rays, emitted by the radioactive element radium) at a sheet of gold foil only 1/3000 of an inch thick, and tracing the particles&apos; paths. Most of the particles went right through the foil, which would be expected if the atoms in the gold were like a plum pudding. But every now and then, a particle bounced back as though it had hit something solid. After tracing many particles and examining the patterns, Rutherford deduced that the atom must have nearly all its mass, and positive charge, in a central nucleus about 10,000 times smaller than the atom itself. All of the negative charge was held in the electrons, which must orbit the dense nucleus like planets around the sun. Ernest Rutherford studied alpha rays, beta rays and gamma rays, emitted by certain radioactive substances. He noticed that each behaved differently in response to an electric field:The b-rays were attracted to the anode The a-rays were attracted to the cathode The g-rays were not affected by the electric field The a and b &quot;rays&quot; were composed of (charged) particles and the g-&quot;ray&quot; was high energy radiation (photons) similar to x-rays b-particles are high speed electrons (charge = -1) a-particles are the positively charged core of the helium atom (charge = +2)
- Goldstein used a gas discharge tube which had a perforated cathode. When a high electrical potential of several thousand volts is applied between the cathode and anode, faint luminous &quot;rays&quot; are seen extending from the holes in the back of the cathode. These rays are beams of particles moving in a direction opposite to the &quot;cathode rays,&quot; which are streams of electrons which move toward the anode. Goldstein called these positive rays Kanalstrahlen, &quot;channel rays&quot; or &quot;canal rays&quot;, because they were produced by the holes or channels in the cathode. In 1907 a study of how this &quot;ray&quot; was deflected in a magnetic field, revealed that the particles making up the ray were not all the same mass. The lightest ones, formed when there was some hydrogen gas in the tube, were calculated to be about 1840 times as massive as an electron. They were protons.
- In 1911, Niels Bohr earned his PhD in Denmark with a dissertation on the electron theory of metals In 1912 Bohr joined Rutherford. He realized that Rutherford&apos;s model wasn&apos;t quite right. By all rules of classical physics, it should be very unstable. For one thing, the orbiting electrons should give off energy and eventually spiral down into the nucleus, making the atom collapse. Or the electrons could be knocked out of position if a charged particle passed by. Bohr turned to Planck&apos;s quantum theory to explain the stability of most atoms. He found that the ratio of energy in electrons and the frequency of their orbits around the nucleus was equal to Planck&apos;s constant (the proportion of light&apos;s energy to its wave frequency, or approximately 6.626 x 10-23 ). Bohr suggested the revolutionary idea that electrons &quot;jump&quot; between energy levels (orbits) in a quantum fashion, that is, without ever existing in an in-between state. Thus when an atom absorbs or gives off energy (as in light or heat), the electron jumps to higher or lower orbits.
- In 1911, Niels Bohr earned his PhD in Denmark with a dissertation on the electron theory of metals In 1912 Bohr joined Rutherford. He realized that Rutherford&apos;s model wasn&apos;t quite right. By all rules of classical physics, it should be very unstable. For one thing, the orbiting electrons should give off energy and eventually spiral down into the nucleus, making the atom collapse. Or the electrons could be knocked out of position if a charged particle passed by. Bohr turned to Planck&apos;s quantum theory to explain the stability of most atoms. He found that the ratio of energy in electrons and the frequency of their orbits around the nucleus was equal to Planck&apos;s constant (the proportion of light&apos;s energy to its wave frequency, or approximately 6.626 x 10-23 ). Bohr suggested the revolutionary idea that electrons &quot;jump&quot; between energy levels (orbits) in a quantum fashion, that is, without ever existing in an in-between state. Thus when an atom absorbs or gives off energy (as in light or heat), the electron jumps to higher or lower orbits.
- Bohr was able to calculate the radii as well energies of the stationary orbit around the nucleus in an atom and those calculated values were found to be in a good agreement with the experimental values. He also gave the Hydrogen ion spectrum. For these reasons, his theory was widely accepted throughout the world. But a few years later, the use of high resolving power spectroscopes revealed some very fine spectral lines which Bohr was not able to explain. So from this point only, Sommerfeld extended Bohr Theory and gave his postulates. According to him, the stationary orbits in which electrons are revolving around the nucleus in the atom are not circular but elliptical in shape. It is due to the influence of the centrally located nucleus. The electron revolves in elliptical path with nucleus at one of its foci. So there will be a major and a minor axis of the path. He said that with the broadening of the orbit, the lengths of the two axis approach to equal value and ultimately become equal i.e. the path become circular. So we can say the circular path is just one special case elliptical path. As electrons travel in elliptical path, it will have an angular momentum and this angular momentum must be quantized according to the quantum theory of radiations. Bohr gave that angular momentum as m=nh/2Ω but Sommerfeld used another integer k instead of n. k is an integer known as azimuthal quantum number.
- In fact, when people refer to &quot;classical physics&quot; today, they mean &quot;before Planck.
- Satyendra Nath Bose had his schooling from Hindu High School in Calcutta. He was a brilliant student. He passed the ISc in 1911 from the Presidency College, Calcutta securing the first position. Satyendra Nath Bose did his BSc in Mathematics from the Presidency College in 1913 and MSc in Mixed Mathematics in 1915 from the same college. He topped the university in BSc. and MSc. Exams. In 1916, the Calcutta University started M.Sc. classes in Modern Mathematics and Modern Physics. S.N. Bose started his career in 1916 as a Lecturer in Physics in Calcutta University. He served here from 1916 to 1921. He joined the newly established Dhaka University in 1921 as a Reader in the Department of Physics.
- E= hv = hc/λ
- But scientists soon realized that the atomic model offered by Rutherford is not complete. Various experiments showed that mass of the nucleus is approximately twice than the number of proton. What is the origin of this additional mass? Rutherford postulated the existence of some neutral particle having mass similar to proton but there was no direct experimental evidence. 1897 Thomson discovers the electron1911 Rutherford discovers the nucleus1932 Chadwick discovers the neutron
- Radium is always radio-nuclide
- The electron neutrino (a lepton) was first postulated in 1930 by Wolfgang Pauli to explain why the electrons in beta decay were not emitted with the full reaction energy of the nuclear transition. The apparent violation of conservation of energy and momentum was most easily avoided by postulating another particle. Enrico Fermi called the particle a neutrino and developed a theory of beta decay based on it, but it was notexperimentally observed until 1956. This elusive particle, with no charge and almost no mass, could penetrate vast thicknesses of material without interaction. The mean free path of a neutrino in water would be on the order of 10x the distance from the Earth to the Sun.
- The Octet Rule was formulated from the observation that atoms with eight valence electrons were especially stable (and common). A similar situation applies to nuclei regarding the number of neutron and proton numbers that generate stable (non-radioactive) isotopes. Thes &quot;magic numbers&quot; are natural occurrences in isotopes that are particularly stable. Table 1 list of numbers of protons and neutrons; isotopes that have these numbers occurring in either the proton or neutron are stable. In some cases there the isotopes can consist of magic numbers for both protons and neutrons; these would be called double magic numbers. The double numbers only occur for isotopes that are heavier, because the repulsion of the forces between the protons.