1) Carl D. Anderson discovered a positively charged particle with a mass similar to an electron's while photographing cosmic ray tracks in a cloud chamber.
2) Analysis of the particle's ionization and energy loss indicated its charge was less than twice and likely equal to the proton's charge. Its mass was less than 20 times an electron's mass.
3) Anderson concluded this was a new fundamental particle, which he named the "positron", the antimatter counterpart to the electron. His discovery helped establish that antimatter exists.
The document discusses various topics related to electromagnetic radiation and quantum mechanics including:
1. Neon signs glow different colors due to gases emitting light at characteristic wavelengths when an electric current passes through.
2. The electromagnetic spectrum consists of radiation with a broad range of wavelengths, including visible light, ultraviolet light, infrared light, microwaves and more.
3. Albert Einstein's photon theory explained the photoelectric effect where photons with sufficient energy can eject electrons from metals.
Atomic emission spectra and the quantum mechanical model Angbii Gayden
1) Atomic emission spectra provide evidence that electrons within atoms can only occupy discrete energy levels. When electrons drop from higher to lower energy levels, they emit photons of light at specific wavelengths, producing lines in the atomic emission spectrum.
2) Max Planck proposed that electromagnetic radiation like light is emitted and absorbed in discrete quanta of energy called photons, where the energy of each photon is directly proportional to its frequency.
3) Albert Einstein applied Planck's quantum theory to explain the photoelectric effect, proposing that light behaves as a particle as well as a wave, with a quantum of energy depending on its frequency.
Nuclear physics involves understanding atoms through experiments like Rutherford's gold foil experiment which showed that atoms have a small, dense nucleus surrounded by empty space. Radiation like alpha, beta, and gamma rays is used in applications such as cancer treatment, electricity generation, and radiocarbon dating which relies on the radioactive decay of carbon-14 to determine the age of ancient materials.
CHAPTER 10 Molecules and Solids
10.1 Molecular Bonding and Spectra
10.2 Stimulated Emission and Lasers
10.3 Structural Properties of Solids
10.4 Thermal and Magnetic Properties of Solids
10.5 Superconductivity
10.6 Applications of Superconductivity
1. The document discusses the development of atomic spectroscopy from 1860 to 1913, including Balmer's empirical formula for the emission spectrum of hydrogen and Bohr's theoretical model of the atom.
2. Bohr postulated that electrons orbit in stable, quantized energy levels and emit or absorb photons of specific frequencies when transitioning between levels.
3. Bohr's model accounted for the Rydberg formula and emission spectrum of hydrogen and was later extended to ions of other elements.
Planck discovered an empirical formula in 1900 that accurately described blackbody radiation spectra across all wavelengths and temperatures. Seeking a physical explanation, he postulated that the walls of a hot cavity contained identical vibrating oscillators that exchange energy with radiation in quantized units proportional to their frequency, called quanta. This quantum hypothesis explained the experimental observations and values Planck calculated for the universal constant h. While initially a mathematical trick, Planck's quantum theory marked a revolutionary beginning of modern quantum mechanics.
- The document discusses quantum theory of radiation and blackbody radiation. It introduces Planck's hypothesis that oscillators can only absorb and emit energy in discrete quanta proportional to frequency to solve the ultraviolet catastrophe.
- Planck's radiation law gives the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium. It was derived using the assumptions that oscillators have discrete energy levels and Boltzmann statistics.
- The Rayleigh-Jeans law, derived from classical physics, correctly predicted blackbody radiation at long wavelengths but failed at short wavelengths, known as the ultraviolet catastrophe. Planck's hypothesis resolved this issue.
The document discusses various topics related to electromagnetic radiation and quantum mechanics including:
1. Neon signs glow different colors due to gases emitting light at characteristic wavelengths when an electric current passes through.
2. The electromagnetic spectrum consists of radiation with a broad range of wavelengths, including visible light, ultraviolet light, infrared light, microwaves and more.
3. Albert Einstein's photon theory explained the photoelectric effect where photons with sufficient energy can eject electrons from metals.
Atomic emission spectra and the quantum mechanical model Angbii Gayden
1) Atomic emission spectra provide evidence that electrons within atoms can only occupy discrete energy levels. When electrons drop from higher to lower energy levels, they emit photons of light at specific wavelengths, producing lines in the atomic emission spectrum.
2) Max Planck proposed that electromagnetic radiation like light is emitted and absorbed in discrete quanta of energy called photons, where the energy of each photon is directly proportional to its frequency.
3) Albert Einstein applied Planck's quantum theory to explain the photoelectric effect, proposing that light behaves as a particle as well as a wave, with a quantum of energy depending on its frequency.
Nuclear physics involves understanding atoms through experiments like Rutherford's gold foil experiment which showed that atoms have a small, dense nucleus surrounded by empty space. Radiation like alpha, beta, and gamma rays is used in applications such as cancer treatment, electricity generation, and radiocarbon dating which relies on the radioactive decay of carbon-14 to determine the age of ancient materials.
CHAPTER 10 Molecules and Solids
10.1 Molecular Bonding and Spectra
10.2 Stimulated Emission and Lasers
10.3 Structural Properties of Solids
10.4 Thermal and Magnetic Properties of Solids
10.5 Superconductivity
10.6 Applications of Superconductivity
1. The document discusses the development of atomic spectroscopy from 1860 to 1913, including Balmer's empirical formula for the emission spectrum of hydrogen and Bohr's theoretical model of the atom.
2. Bohr postulated that electrons orbit in stable, quantized energy levels and emit or absorb photons of specific frequencies when transitioning between levels.
3. Bohr's model accounted for the Rydberg formula and emission spectrum of hydrogen and was later extended to ions of other elements.
Planck discovered an empirical formula in 1900 that accurately described blackbody radiation spectra across all wavelengths and temperatures. Seeking a physical explanation, he postulated that the walls of a hot cavity contained identical vibrating oscillators that exchange energy with radiation in quantized units proportional to their frequency, called quanta. This quantum hypothesis explained the experimental observations and values Planck calculated for the universal constant h. While initially a mathematical trick, Planck's quantum theory marked a revolutionary beginning of modern quantum mechanics.
- The document discusses quantum theory of radiation and blackbody radiation. It introduces Planck's hypothesis that oscillators can only absorb and emit energy in discrete quanta proportional to frequency to solve the ultraviolet catastrophe.
- Planck's radiation law gives the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium. It was derived using the assumptions that oscillators have discrete energy levels and Boltzmann statistics.
- The Rayleigh-Jeans law, derived from classical physics, correctly predicted blackbody radiation at long wavelengths but failed at short wavelengths, known as the ultraviolet catastrophe. Planck's hypothesis resolved this issue.
Ernest Rutherford's alpha ray scattering experiment led him to propose the nuclear model of the atom. The key findings were:
1) Most alpha particles passed through the thin gold foil with little deflection, but a small percentage were deflected by large angles, including backwards.
2) This could only be explained if the positive charge of the atom was concentrated into a very small, dense nucleus.
3) Rutherford concluded atoms have a small, dense nucleus containing its positive charge and mass, with electrons orbiting the nucleus.
This nuclear model replaced the plum pudding model, but had its own limitations that were later addressed by Niels Bohr's model of electron orbits and quantization
This document provides an overview of radiation heat transfer and outlines the course content for an undergraduate course on the topic. It discusses key concepts such as blackbody radiation, Planck's law, Stefan-Boltzmann law, and Wien's displacement law. Example problems are provided to illustrate calculating the spectral and total emissive power of blackbody radiation sources. The summary highlights that radiation transfer does not require a medium, occurs at the speed of light, and that surfaces behave as blackbodies when enclosed in an isothermal cavity.
The document provides a history of the development of atomic structure models from ancient Greek philosophers' ideas of indivisible atoms to the modern quantum mechanical model. It describes key experiments and findings such as Thomson's discovery of electrons, Rutherford's gold foil experiment, and Bohr's model of electron orbits that led to modern atomic theory. The emission spectra of elements provided evidence that electrons exist in specific energy levels and orbitals within atoms.
1) The document discusses the photoelectric effect and early explanations provided by Planck's quantum theory and Einstein. It describes experiments showing that electrons are emitted from metals when light above a threshold frequency strikes them.
2) Einstein used Planck's idea that energy is emitted and absorbed in discrete quanta to explain the photoelectric effect. He proposed that light consists of discrete packets of energy called photons, and that photons impart their entire energy to electrons.
3) The document also discusses de Broglie's hypothesis that all matter exhibits wave-particle duality, and derives an expression for the de Broglie wavelength of matter particles.
This document provides information about Niels Bohr's model of the atom. It discusses that Bohr's model postulated that electrons revolve around the nucleus in definite circular orbits called energy levels. Electrons can move between these levels by absorbing or emitting energy. The model helped explain atomic spectra but had limitations and could not explain more complex atoms or finer details of spectral lines.
The document discusses light interaction with atoms and molecules, including:
1) Atomic spectra such as the Balmer series arise from electrons falling to lower energy levels in hydrogen atoms.
2) More complex atoms like sodium and mercury require additional quantum numbers to describe their emission spectra.
3) Simple molecules like hydrogen absorb UV light when electrons are promoted between molecular orbitals.
4) Conjugated systems and heteroatoms in molecules like butadiene and formaldehyde shift absorption to longer wavelengths.
Ion traps offer a possible solution to the challenge of building a quantum computer by isolating ions as physical qubits. Ion traps use oscillating electric fields to confine ions in a line, isolating them from the environment while still allowing for manipulation and interaction through laser beams and the Coulomb force. The linear Paul trap in particular was inspired by Wolfgang Paul observing eggs on a tray and forms the basis for trapped ion quantum computation.
This paper shows my findings for determining the grating constant of a diffraction grating, the wavelengths of each line of the spectrum of hydrogen, and experimentally calculating the Rydberg constant.
How the Bohr Model of the Atom Accounts for Limitations with Classical Mechan...Thomas Oulton
This small essay concisely outlines how Classical mechanics was deemed unacceptable when describing the motions of electrons within an atom through the observations made by hydrogen spectra, and how this lead to a revolution in atomic theory. Included is a brief overview of how Bohr arrived at his model through applying quantum mechanics.
Written for; First year Undergraduate study,
Materials Science and Engineering,
The University of Sheffield
Graded at 78%
Planck's Quantum Theory and Discovery of X-raysSidra Javed
Planck's quantum theory
Discovery of X-rays and explanation of production of X-rays, relation between atomic number and frequency of X-rays, application and uses of X-rays.
The document is about the structure of an atom according to an 11th grade student named Shubham Kumar. It discusses that an atom is composed of a nucleus containing protons and neutrons, and electrons orbiting the nucleus. It also explains that protons have a positive charge, neutrons have no charge, and electrons have a negative charge, making the total charge of a neutral atom zero. The document then provides more details about the atomic nucleus, isotopes, electron configuration, and types of nuclear decay.
B.Tech sem I Engineering Physics U-IV Chapter 1-ATOMIC PHYSICSAbhi Hirpara
Atomic physics describes phenomena at the scale of atoms and subatomic particles. It emerged in the early 20th century to address limitations in classical physics' ability to describe certain phenomena. Quantum physics recognizes that there is less difference between waves and particles than previously thought. It is probabilistic and counterintuitive, describing particles that can behave as waves and vice versa. Quantum physics underlies our understanding of atomic and subatomic systems and is crucial to fields like chemistry, materials science, and astrophysics. Planck's quantum hypothesis proposed that atoms can only absorb or emit energy in discrete quanta, initiating the development of quantum theory. Einstein later theorized that electromagnetic radiation consists of discrete photon particles, helping explain the photoelectric effect.
The document discusses several topics in atomic and nuclear physics including:
1) The photoelectric effect describes how light shining on a metal surface can eject electrons. Compton scattering demonstrates that X-rays lose energy when scattered by electrons, showing the particle nature of light.
2) X-rays are produced when high-energy electrons collide with atoms, either ejecting inner electrons or through braking radiation when deflected by the nucleus.
3) Light exhibits both wave and particle properties in experiments like the photoelectric effect, Compton scattering, and the Young's interference experiment, known as wave-particle duality.
4) Electrons falling between energy levels emit photons with energy equal to the level difference
Quantum Mechanics: Electrons, Transistors, & LASERS. Paul H. Carr
Quantum Mechanics, QM, has enabled new technologies that impact our daily lives. Yet, there have been at least 14 different QM interpretations in the last century. “If you think you understand QM, you don’t,” said Richard Feynman. Our macroscopic language is inadequate to describe the wave-particle duality of microscopic QM particles. Mathematics works better. This talk illuminated the production of the play Copenhagen, in which German physicist Werner Heisenberg, who directed the German attempt to make an atom bomb, visited Niels Bohr in Denmark during WWII.
M.Sc.Part-II Sem- III (Unit - IV) Nuclear Magnetic Resonance Spectroscopypramod padole
This document provides an overview of nuclear magnetic resonance (NMR) spectroscopy. It begins with definitions and basic principles of NMR, including how nuclei absorb radio frequencies in a magnetic field. It then discusses NMR instrumentation and the effects of chemical equivalence and spin splitting on NMR signals. The document outlines the contents to be covered, including principles of NMR, instrumentation, chemical equivalence, splitting of signals, and practice problems. It aims to discuss practical aspects of NMR and its application in solving structures of organic molecules.
The document discusses several key concepts relating to blackbody radiation:
1) A blackbody is an idealized object that absorbs all electromagnetic radiation falling on it without reflecting or transmitting any.
2) The purpose of the experiment was to measure the intensity of electromagnetic waves emitted by a blackbody as its temperature increases, and to use Wien's and Stephan Boltzmann's laws.
3) The experiment had many flaws and issues, resulting in unreliable data that did not match theoretical predictions.
1) Nuclear fusion and fission reactions can release large amounts of energy. Fusion occurs when light nuclei join together, as in the Sun, while fission occurs when heavy nuclei split apart.
2) A graph of binding energy per nucleon shows that mid-sized nuclei are most stable, and that both fission and fusion reactions produce fragments with higher binding energy, releasing energy.
3) Nuclear fission in uranium can be triggered by neutrons and produce a chain reaction releasing many neutrons, as used in nuclear weapons and controlled in nuclear power plants. Nuclear fusion is even more powerful but requires extremely high temperatures and pressures to overcome repulsion between positively charged nuclei.
This document discusses atomic, nuclear and particle physics concepts including:
1. Discrete energy levels in atoms lead to line spectra fingerprints of elements. Electrons can only have certain quantized energy levels and jump between them, emitting photons of specific wavelengths.
2. The Bohr model of the atom helped explain line spectra by proposing electrons orbit nuclei in fixed, quantized energy levels. Electron transitions between levels emit or absorb photons of specific energies.
3. Atoms are composed of a nucleus containing protons and neutrons. Isotopes are atoms of the same element with different numbers of neutrons. Evidence for neutrons comes from isotopes having the same number of protons but different masses.
4. Radio
Quantum theory describes the behavior of small particles like electrons and photons. It seems counterintuitive because particles can act like waves and exist in multiple states at once until observed. The theory was developed between 1900-1930 and helped establish modern physics. It includes ideas like wave-particle duality, Heisenberg's uncertainty principle, and quantum fluctuations that allow particles to briefly exist from nothing. While still incomplete, quantum theory is well-supported by evidence and critical to technologies like computers.
Ernst Rutherford conducted an experiment where he had Geiger and Marsden fire alpha particles at a thin gold foil. Most passed through but some were scattered back, surprising Rutherford. He realized the positive charge in atoms must be highly concentrated in the nucleus to repel the positively charged alpha particles. This led to Rutherford's nuclear model of the atom, where the tiny, dense nucleus contains most of the atom's mass and positive charge, and electrons orbit at a relatively large distance. Later, the discovery of the neutron by Chadwick completed the picture of protons and neutrons in the atomic nucleus.
In your previous class you have already studies about the structure of an atom but some of the exception you can learn here in this chapter how the structure of an atom is fully defined
1) Experiments with cathode ray tubes led to the discovery of the electron as a negatively charged fundamental particle.
2) Further experiments showed that atoms are mostly empty space and contain a small, dense nucleus made up of protons and neutrons, around which electrons orbit.
3) The photoelectric effect showed that light behaves as a particle (photon) rather than just a wave, transferring its energy in discrete quantized amounts to electrons and ejecting them from metal surfaces.
Ernest Rutherford's alpha ray scattering experiment led him to propose the nuclear model of the atom. The key findings were:
1) Most alpha particles passed through the thin gold foil with little deflection, but a small percentage were deflected by large angles, including backwards.
2) This could only be explained if the positive charge of the atom was concentrated into a very small, dense nucleus.
3) Rutherford concluded atoms have a small, dense nucleus containing its positive charge and mass, with electrons orbiting the nucleus.
This nuclear model replaced the plum pudding model, but had its own limitations that were later addressed by Niels Bohr's model of electron orbits and quantization
This document provides an overview of radiation heat transfer and outlines the course content for an undergraduate course on the topic. It discusses key concepts such as blackbody radiation, Planck's law, Stefan-Boltzmann law, and Wien's displacement law. Example problems are provided to illustrate calculating the spectral and total emissive power of blackbody radiation sources. The summary highlights that radiation transfer does not require a medium, occurs at the speed of light, and that surfaces behave as blackbodies when enclosed in an isothermal cavity.
The document provides a history of the development of atomic structure models from ancient Greek philosophers' ideas of indivisible atoms to the modern quantum mechanical model. It describes key experiments and findings such as Thomson's discovery of electrons, Rutherford's gold foil experiment, and Bohr's model of electron orbits that led to modern atomic theory. The emission spectra of elements provided evidence that electrons exist in specific energy levels and orbitals within atoms.
1) The document discusses the photoelectric effect and early explanations provided by Planck's quantum theory and Einstein. It describes experiments showing that electrons are emitted from metals when light above a threshold frequency strikes them.
2) Einstein used Planck's idea that energy is emitted and absorbed in discrete quanta to explain the photoelectric effect. He proposed that light consists of discrete packets of energy called photons, and that photons impart their entire energy to electrons.
3) The document also discusses de Broglie's hypothesis that all matter exhibits wave-particle duality, and derives an expression for the de Broglie wavelength of matter particles.
This document provides information about Niels Bohr's model of the atom. It discusses that Bohr's model postulated that electrons revolve around the nucleus in definite circular orbits called energy levels. Electrons can move between these levels by absorbing or emitting energy. The model helped explain atomic spectra but had limitations and could not explain more complex atoms or finer details of spectral lines.
The document discusses light interaction with atoms and molecules, including:
1) Atomic spectra such as the Balmer series arise from electrons falling to lower energy levels in hydrogen atoms.
2) More complex atoms like sodium and mercury require additional quantum numbers to describe their emission spectra.
3) Simple molecules like hydrogen absorb UV light when electrons are promoted between molecular orbitals.
4) Conjugated systems and heteroatoms in molecules like butadiene and formaldehyde shift absorption to longer wavelengths.
Ion traps offer a possible solution to the challenge of building a quantum computer by isolating ions as physical qubits. Ion traps use oscillating electric fields to confine ions in a line, isolating them from the environment while still allowing for manipulation and interaction through laser beams and the Coulomb force. The linear Paul trap in particular was inspired by Wolfgang Paul observing eggs on a tray and forms the basis for trapped ion quantum computation.
This paper shows my findings for determining the grating constant of a diffraction grating, the wavelengths of each line of the spectrum of hydrogen, and experimentally calculating the Rydberg constant.
How the Bohr Model of the Atom Accounts for Limitations with Classical Mechan...Thomas Oulton
This small essay concisely outlines how Classical mechanics was deemed unacceptable when describing the motions of electrons within an atom through the observations made by hydrogen spectra, and how this lead to a revolution in atomic theory. Included is a brief overview of how Bohr arrived at his model through applying quantum mechanics.
Written for; First year Undergraduate study,
Materials Science and Engineering,
The University of Sheffield
Graded at 78%
Planck's Quantum Theory and Discovery of X-raysSidra Javed
Planck's quantum theory
Discovery of X-rays and explanation of production of X-rays, relation between atomic number and frequency of X-rays, application and uses of X-rays.
The document is about the structure of an atom according to an 11th grade student named Shubham Kumar. It discusses that an atom is composed of a nucleus containing protons and neutrons, and electrons orbiting the nucleus. It also explains that protons have a positive charge, neutrons have no charge, and electrons have a negative charge, making the total charge of a neutral atom zero. The document then provides more details about the atomic nucleus, isotopes, electron configuration, and types of nuclear decay.
B.Tech sem I Engineering Physics U-IV Chapter 1-ATOMIC PHYSICSAbhi Hirpara
Atomic physics describes phenomena at the scale of atoms and subatomic particles. It emerged in the early 20th century to address limitations in classical physics' ability to describe certain phenomena. Quantum physics recognizes that there is less difference between waves and particles than previously thought. It is probabilistic and counterintuitive, describing particles that can behave as waves and vice versa. Quantum physics underlies our understanding of atomic and subatomic systems and is crucial to fields like chemistry, materials science, and astrophysics. Planck's quantum hypothesis proposed that atoms can only absorb or emit energy in discrete quanta, initiating the development of quantum theory. Einstein later theorized that electromagnetic radiation consists of discrete photon particles, helping explain the photoelectric effect.
The document discusses several topics in atomic and nuclear physics including:
1) The photoelectric effect describes how light shining on a metal surface can eject electrons. Compton scattering demonstrates that X-rays lose energy when scattered by electrons, showing the particle nature of light.
2) X-rays are produced when high-energy electrons collide with atoms, either ejecting inner electrons or through braking radiation when deflected by the nucleus.
3) Light exhibits both wave and particle properties in experiments like the photoelectric effect, Compton scattering, and the Young's interference experiment, known as wave-particle duality.
4) Electrons falling between energy levels emit photons with energy equal to the level difference
Quantum Mechanics: Electrons, Transistors, & LASERS. Paul H. Carr
Quantum Mechanics, QM, has enabled new technologies that impact our daily lives. Yet, there have been at least 14 different QM interpretations in the last century. “If you think you understand QM, you don’t,” said Richard Feynman. Our macroscopic language is inadequate to describe the wave-particle duality of microscopic QM particles. Mathematics works better. This talk illuminated the production of the play Copenhagen, in which German physicist Werner Heisenberg, who directed the German attempt to make an atom bomb, visited Niels Bohr in Denmark during WWII.
M.Sc.Part-II Sem- III (Unit - IV) Nuclear Magnetic Resonance Spectroscopypramod padole
This document provides an overview of nuclear magnetic resonance (NMR) spectroscopy. It begins with definitions and basic principles of NMR, including how nuclei absorb radio frequencies in a magnetic field. It then discusses NMR instrumentation and the effects of chemical equivalence and spin splitting on NMR signals. The document outlines the contents to be covered, including principles of NMR, instrumentation, chemical equivalence, splitting of signals, and practice problems. It aims to discuss practical aspects of NMR and its application in solving structures of organic molecules.
The document discusses several key concepts relating to blackbody radiation:
1) A blackbody is an idealized object that absorbs all electromagnetic radiation falling on it without reflecting or transmitting any.
2) The purpose of the experiment was to measure the intensity of electromagnetic waves emitted by a blackbody as its temperature increases, and to use Wien's and Stephan Boltzmann's laws.
3) The experiment had many flaws and issues, resulting in unreliable data that did not match theoretical predictions.
1) Nuclear fusion and fission reactions can release large amounts of energy. Fusion occurs when light nuclei join together, as in the Sun, while fission occurs when heavy nuclei split apart.
2) A graph of binding energy per nucleon shows that mid-sized nuclei are most stable, and that both fission and fusion reactions produce fragments with higher binding energy, releasing energy.
3) Nuclear fission in uranium can be triggered by neutrons and produce a chain reaction releasing many neutrons, as used in nuclear weapons and controlled in nuclear power plants. Nuclear fusion is even more powerful but requires extremely high temperatures and pressures to overcome repulsion between positively charged nuclei.
This document discusses atomic, nuclear and particle physics concepts including:
1. Discrete energy levels in atoms lead to line spectra fingerprints of elements. Electrons can only have certain quantized energy levels and jump between them, emitting photons of specific wavelengths.
2. The Bohr model of the atom helped explain line spectra by proposing electrons orbit nuclei in fixed, quantized energy levels. Electron transitions between levels emit or absorb photons of specific energies.
3. Atoms are composed of a nucleus containing protons and neutrons. Isotopes are atoms of the same element with different numbers of neutrons. Evidence for neutrons comes from isotopes having the same number of protons but different masses.
4. Radio
Quantum theory describes the behavior of small particles like electrons and photons. It seems counterintuitive because particles can act like waves and exist in multiple states at once until observed. The theory was developed between 1900-1930 and helped establish modern physics. It includes ideas like wave-particle duality, Heisenberg's uncertainty principle, and quantum fluctuations that allow particles to briefly exist from nothing. While still incomplete, quantum theory is well-supported by evidence and critical to technologies like computers.
Ernst Rutherford conducted an experiment where he had Geiger and Marsden fire alpha particles at a thin gold foil. Most passed through but some were scattered back, surprising Rutherford. He realized the positive charge in atoms must be highly concentrated in the nucleus to repel the positively charged alpha particles. This led to Rutherford's nuclear model of the atom, where the tiny, dense nucleus contains most of the atom's mass and positive charge, and electrons orbit at a relatively large distance. Later, the discovery of the neutron by Chadwick completed the picture of protons and neutrons in the atomic nucleus.
In your previous class you have already studies about the structure of an atom but some of the exception you can learn here in this chapter how the structure of an atom is fully defined
1) Experiments with cathode ray tubes led to the discovery of the electron as a negatively charged fundamental particle.
2) Further experiments showed that atoms are mostly empty space and contain a small, dense nucleus made up of protons and neutrons, around which electrons orbit.
3) The photoelectric effect showed that light behaves as a particle (photon) rather than just a wave, transferring its energy in discrete quantized amounts to electrons and ejecting them from metal surfaces.
Structure Of Atom_STUDY MATERIALS_JEE-MAIN_AIPMTSupratim Das
1. Dalton's atomic theory proposed that atoms are indivisible, hard spheres that differ in properties based on their unique structure.
2. Rutherford's gold foil experiment showed that atoms have a small, dense nucleus containing their mass, with electrons orbiting the nucleus.
3. Bohr used Planck's quantum theory to explain electron orbits in hydrogen atoms, stabilizing Rutherford's model and beginning modern atomic theory.
This document discusses the discovery of artificial radioactivity by Curie and Joliot in 1934. When boron and aluminum were bombarded with alpha particles, the target nuclei continued emitting radiation even after the alpha source was removed. Through experiments, they determined the radiation consisted of positrons, positively charged particles with mass equal to electrons. Curie and Joliot explained that bombarding the elements created unstable nuclei that spontaneously disintegrated. For boron, this produced radioactive nitrogen that decayed to stable carbon with a half-life of 10.1 minutes by emitting a positron. For aluminum, it produced radioactive phosphorus with a half-life of about 3 minutes that decayed to stable phosphorus. This demonstrated the
1. The document discusses the discovery of the electron through cathode ray experiments and the determination of the charge to mass ratio of electrons.
2. Rutherford's alpha particle scattering experiments showed that the atom has a small, dense nucleus containing positive charge and mass, surrounded by electrons. This led to the development of the Rutherford model of the atom.
3. The document also discusses the discovery of protons and neutrons, atomic number and mass number, isotopes, drawbacks of the Rutherford model, wave-particle duality of light, and Planck's quantum theory.
3.1 Discovery of the X Ray and the Electron
3.2 Determination of Electron Charge
3.3 Line Spectra
3.4 Quantization
3.5 Blackbody Radiation
3.6 Photoelectric Effect
3.7 X-Ray Production
3.8 Compton Effect
3.9 Pair Production and Annihilation
The document summarizes key concepts about atomic structure and models. It discusses experiments that led to discoveries of the electron and properties like charge/mass ratio. Models proposed include Thomson's plum pudding model and Rutherford's nuclear model. Planck's quantum theory explained blackbody radiation and the photoelectric effect. Max Planck suggested that energy is quantized and comes in discrete packets called quanta.
The document discusses Rutherford's experiment in 1909 where he investigated alpha particles passing through thin metal foils. The experiment found that a small percentage of alpha particles were deflected at very high angles, contrary to expectations based on Thomson's atom model. This led Rutherford to propose the nuclear model of the atom with a small, dense nucleus at the center containing positive charge and mass. It also discusses nuclear energy levels, radioactive decay processes including beta decay and neutrinos, and the use of mass spectrometers to determine atomic mass.
1) The document provides a summary of a course on high-energy astrophysics that the author took. It discusses various topics covered in the course including accretion disks, pulsars, black holes, supernovae, and more.
2) The author argues that high-energy astrophysics is important for understanding the universe and requests that the provost offer a similar course at their university.
3) Key concepts in high-energy astrophysics discussed include accretion and its relation to luminosity, binary star systems, properties of neutron stars and black holes, and x-ray emissions from astrophysical phenomena like supernovae.
Ernst Goldstein discovered positive rays (protons) in 1886 by passing cathode rays through a perforated cathode. Positive rays were produced and carried a positive charge. J.J. Thomson later determined the e/m ratio of protons depends on the gas used, with hydrogen giving the maximum ratio and identifying the lightest particle as the proton. In 1932, James Chadwick discovered the neutron through bombarding beryllium with alpha particles. The neutron was later found to be neutral and able to induce nuclear reactions. Rutherford proposed atoms consisted of electrons and protons in 1911 based on alpha scattering experiments, but the planetary model was defective as it did not explain the stability of electron orbits.
Rutherford's scattering experiments showed that atoms have a small, dense nucleus surrounded by electrons. This contradicted Thomson's "plum pudding" model and led to Rutherford proposing a planetary model of the atom. However, the planetary model is unstable because orbiting electrons would radiate energy according to Maxwell's equations and lose orbit. Spectroscopy experiments produced line spectra that needed to be explained by a new atomic model. Bohr proposed a new quantum mechanical model of the hydrogen atom that could account for its line spectrum.
1. World Environment Day 2020 will be hosted in Colombia in partnership with Germany, with the theme of biodiversity.
2. During lockdowns due to the coronavirus pandemic, pollution levels decreased as industries shut down and traffic reduced, showing nature's power to recover if given the chance.
3. World Environment Day, celebrated annually on June 5th, aims to raise awareness of environmental protection.
1) The document discusses several topics in quantum mechanics including Planck's law, Wien's law, Rayleigh-Jeans law, Compton scattering, the Compton effect, de Broglie's hypothesis of matter waves, and the Davisson-Germer experiment.
2) It explains that Compton scattering results in a shift in wavelength when X-rays interact with electrons. Compton treated this as particle collision between photons and electrons.
3) The Davisson-Germer experiment in 1927 provided the first evidence of matter waves by observing interference patterns when electrons were diffracted by a nickel crystal, supporting de Broglie's hypothesis that particles can behave as waves.
This document summarizes an experiment on gamma ray spectroscopy and attenuation. Key findings include:
1) Gamma ray emission spectra were collected for isotopes 22Na, 60Co, 137Cs, and 133Ba and a mystery isotope was identified as 232Th.
2) Exponential attenuation models were tested for 137Cs and 60Co interacting with lead, aluminum, and graphite. The model was rejected for 137Cs but not for 60Co.
3) Mass attenuation coefficients were determined for the absorbing materials using photopeak photometry data from 137Cs and 60Co.
1. Dalton's atomic theory proposed that matter consists of indivisible atoms and that atoms of different elements differ in mass. Compounds are formed by atoms combining in fixed ratios.
2. Rutherford's gold foil experiment showed that the positive charge and mass of an atom are concentrated in a very small nucleus, with electrons orbiting the nucleus.
3. The discovery of subatomic particles like electrons, protons, and neutrons led to modifications of atomic structure, with atoms composed of a nucleus surrounded by electrons.
The document discusses the history of atomic structure models from Democritus' idea of atoms to Bohr's model. Some key points:
1. J.J. Thomson's experiments in 1897 led him to propose the "plum pudding" model where electrons were embedded in a uniform positive charge.
2. Rutherford's gold foil experiment in 1911 showed that the atom has a small, dense, positively charged nucleus at its center.
3. Bohr modified Rutherford's model in 1913 to propose that electrons orbit the nucleus in discrete energy levels, explaining atomic line spectra. When electrons fall from higher to lower orbits, photons are emitted.
Production and Emission of X-Rays - Sultan LeMarcslemarc
This document describes an experiment to investigate the production and emission of x-rays. It will measure the count rate of x-rays reflected off a lithium fluoride crystal at varying angles to determine the characteristic peaks and wavelength of copper using Bragg's law. It will also examine the absorption of homogeneous x-rays by measuring the relationship between intensity and count rate. The document provides background on x-ray production, emission spectra, Bragg diffraction, and absorption. It describes using a Tel-X-Ometer device to measure count rates at different scattering angles in order to analyze the diffraction patterns.
The document discusses the structure and composition of atoms and elementary particles. It describes how atoms are made up of even smaller particles like electrons, protons, and neutrons. Protons and neutrons are made up of even smaller particles called quarks. The smallest known particles are the six types of quarks and six types of leptons that make up all hadrons and compose all visible matter in the universe according to the Standard Model of particle physics.
Ion cyclotron resonance spectroscopy and photo acoustic spectroscopymanikanthaTumarada
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Anderson and the Positron
1. Carl D. Anderson Phys. Rev. 43, 491 1933
The Positive Electron
CARL D. ANDERSON,
California Institute of Technology, Pasadena, California
(Received February 28, 1933)
Abstract
Out of a group of 1300 photographs of cosmic-ray tracks in a ver-
tical Wilson chamber 15 tracks were of positive particles which could
not have a mass as great as that of the proton. From an examina-
tion of the energy-loss and ionization produced it is concluded thai the
charge is less than twice, and is probably exactly equal to, that of the
proton. If these particles carry unit positive charge the curvatures and
ionizations produced require the mass to be less than twenty times the
electron mass. These particles will be called positrons. Because they
occur in groups associated with other tracks it is concluded that they
must be secondary particles ejected from atomic nuclei.
Editor
On August 2, 1932, during the course of photographing cosmic-ray tracks
produced in a vertical Wilson chamber (magnetic field of 15,000 gauss) de-
signed in the summer of 1930 by Professor R. A. Millikan and the writer,
the tracks shown in Fig. 1 were obtained, which seemed to be interpretable
only on the basis of the existence in this case of a particle carrying a positive
charge but having a mass of the same order of magnitude as that normally
possessed by a free negative electron. Later study of the photograph by
a whole group of men of the Norman Bridge Laboratory only tended to
strengthen this view. The reason that this interpretation seemed so in-
evitable is that the track appearing on the upper half of the figure cannot
possibly have a mass as large as that of a proton for as soon as the mass is
fixed the energy is at once fixed by the curvature. The energy of a proton of
that curvature comes out 300,000 volts, but a proton of that energy accord-
1
2. ing to well established and universally accepted determinations1 has a total
range of about 5 mm in air while that portion of the range actually visible in
this case exceeds 5 cm without a noticeable change in curvature. The only
escape from this conclusion would be to assume that at exactly the same
instant (and the sharpness of the tracks determines that instant to within
about a fiftieth of a second) two independent electrons happened to produce
two tracks so placed as to give the impression of a single particle shooting
through the lead plate. This assumption was dismissed on a probability
basis, since a sharp track of this order of curvature under the experimental
conditions prevailing occurred in the chamber only once in some 500 expo-
sures, and since there was practically no chance at all that two such tracks
should line up in this way. We also discarded as completely untenable the
assumption of an electron of 20 million volts entering the lead on one side
and coming out with an energy of 60 million volts on the other side. A
fourth possibility is that a photon, entering the lead from above, knocked
out of the nucleus of a lead atom two particles, one of which shot upward
and the other downward. But in this case the upward moving one would be
a positive of small mass so that either of the two possibilities leads to the
existence of the positive electron.
In the course of the next few weeks other photographs were obtained
which could be interpreted logically only on the positive-electron basis, and
a brief report was then published2 with due reserve in interpretation in view
of the importance and striking nature of the announcement.
1 MAGNITUDE OF CHARGE AND MASS
It is possible with the present experimental data only to assign rather wide
limits to the magnitude of the charge and mass of the particle. The specific
ionization was not in these cases measured, but it appears very probable,
from a knowledge of the experimental conditions and by comparison with
many other photographs of high- and low-speed electrons taken under the
same conditions, that the charge cannot differ in magnitude from that of
an electron by an amount as great as a factor of two. Furthermore, if the
photograph is taken to represent a positive particle penetrating the 6 mm
lead plate, then the energy lost, calculated for unit charge, is approximately
1
Rutherford, Chadwick and Ellis, Radiations from Radioactive Substances, p. 294.
Assuming Rαv 3 and using data there given the range of a 300,000 volt proton in air
S.T.P. is about 5 mm.
2
C. D. Anderson, Science 76, 238 (1932).
2
3. Figure 1: A 63 million volt positron (Hρ = 2.1 × 105 gauss-cm) passing
through a 6 mm lead plate and emerging as a 23 million volt positron (Hρ =
7.5×104 gauss-cm). The length of this latter path is at least ten times greater
than the possible length of a proton path of this curvature.
3
4. Figure 2: A positron of 20 million volts energy (Hρ = 7.1 × 104 gauss-
cm) and a negatron of 30 million volts energy (Hρ = 10.2 × 104 gauss-cm)
projected from a plate of lead. The range of the positive particle precludes
the possibility of ascribing it to a proton of the observed curvature.
38 million electron-volts, this value being practically independent of the
proper mass of the particle as long as it is not too many times larger than
that of a free negative electron. This value of 63 million volts per cm energy-
loss for the positive particle it was considered legitimate to compare with
the measured mean of approximately 35 million volts3 for negative electrons
of 200-300 million volts energy since the rate of energy-loss for particles of
small mass is expected to change only very slowly over an energy range
extending from several million to several hundred million volts. Allowance
being made for experimental uncertainties, an upper limit to the rate of loss
of energy for the positive particle can then be set at less than four times that
for an electron, thus fixing, by the usual relation between rate of ionization
and charge, an upper limit to the charge less than twice that of the negative
electron. It is concluded, therefore, that the magnitude of the charge of
the positive electron which we shall henceforth contract to positron is very
probably equal to that of a free negative electron which from symmetry
considerations would naturally then be called a negatron.
It is pointed out that the effective depth of the chamber in the line of
sight which is the same as the direction of the magnetic lines of force was 1
3
C. D. Anderson, Phys. Rev. 43, 381A (1933).
4
5. cm and its effective diameter at right angles to that line 14 cm, thus insuring
that the particle crossed the chamber practically normal to the lines of force.
The change in direction due to scattering in the lead4 , in this case about 8◦
measured in the plane of the chamber, is a probable value for a particle of
this energy though less than the most probable value.
The magnitude of the proper mass cannot as yet be given further than to
fix an upper limit to it about twenty times that of the electron mass. If Fig.
1 represents a particle of unit charge passing through the lead plate then
the curvatures, on the basis of the information at hand on ionization, give
too low a value for the energy-loss unless the mass is taken less than twenty
times that of the negative electron mass. Further determinations of Hρ for
relatively low energy particles before and after they cross a known amount
of matter, together with a study of ballistic effects such as close encounters
with electrons, involving large energy transfers, will enable closer limits to
be assigned to the mass.
To date, out of a group of 1300 photographs of cosmic-ray. tracks 15
of these show positive particles penetrating the lead, none of which can
be ascribed to particles with a mass as large as that of a proton, thus
establishing the existence of positive particles of unit charge and of mass
small compared to that of a proton. In many other cases due either to the
short section of track available for measurement or to the high energy of
the particle it is not possible to differentiate with certainty between protons
and positrons. A comparison of the six or seven hundred positive-ray tracks
which we have taken is, however, still consistent with the view that the
positive particle which is knocked out of the nucleus by the incoming primary
cosmic ray is in many cases a proton.
From the fact that positrons occur in groups associated with other tracks
it is concluded that they must be secondary particles ejected from an atomic
nucleus. If we retain the view that a nucleus consists of protons and neutrons
(and α− particles) and that a neutron represents a close combination of a
proton and electron, then from the electromagnetic theory as to the origin of
mass the simplest assumption would seem to be that an encounter between
the incoming primary ray and a proton may take place in such a way as
to expand the diameter of the proton to the same value as that possessed
by the negatron. This process would release an energy of a billion electron-
volts appearing as a secondary photon. As a second possibility the primary
ray may disintegrate a neutron (or more than one) in the nucleus by the
ejection either of a negatron or a positron with the result that a positive or
4
C. D. Anderson, Phys. Rev. 43, 381A (1933).
5
6. Figure 3: A group of six particles projected from a region in the wall of
the chamber. The track at the left of the central group of four tracks is a
negatron of about 18 million volts energy (Hρ = 6.2×104 gauss-cm) and that
at the right a positron of about 20 million volts energy (Hρ = 7.0×104 gauss-
cm). Identification of the two tracks in the center is not possible. A negatron
of about 15 million volts is shown at the left. This group represents early
tracks which were broadened by the diffusion of the ions. The uniformity
of this broadening for all the tracks shows that the particles entered the
chamber at the same time.
6
7. Figure 4: A positron of about 200 million volts energy (Hρ = 6.6 × 105
gauss-cm) penetrates the 11 mm lead plate and emerges with about 125
million volts energy (Hρ = 4.2 × 105 gauss-cm). The assumption that the
tracks represent a proton traversing the lead plate is inconsistent with the
observed curvatures. The energies would then be, respectively, about 20
million and 8 million volts above and below the lead, energies too low to
permit the proton to have a range sufficient to penetrate a plate of lead of
11 mm thickness.
a negative proton, as the case may be, remains in the nucleus in place of
the neutron, the event occurring in this instance without the emission of a
photon. This alternative, however, postulates the existence in the nucleus
of a proton of negative charge, no evidence for which exists. The greater
symmetry, however, between the positive and negative charges revealed by
the discovery of the positron should prove a stimulus to search for evidence
of the existence of negative protons. If the neutron should prove to be
a fundamental particle of a new kind rather than a proton and negatron
in close combination, the above hypotheses will have to be abandoned for
the proton will then in all probability be represented as a complex particle
consisting of a neutron and positron.
7
8. While this paper was in preparation press reports have announced that
P. M. S. Blackett and G. Occhialini in an extensive study of cosmic-ray
tracks have also obtained evidence for the existence of light positive particles
confirming our earlier report.
I wish to express my great indebtedness to Professor R. A. Millikan for
suggesting this research and for many helpful discussions during its progress.
The able assistance of Mr. Seth H. Neddermeyer is also appreciated.
8