is non-zero‚ unlike an insulator‚ yet still several magnitudes smaller than that of a conductor. There exists a significant energy gap between the filled valence – highest range of electron energies normally present at absolute zero – and empty conduction bands – range of energies which are enough to unbind the electron from the atom and allow it to move freely within the atomic lattice – in a semiconductor‚ unlike a conductor which has very small or no band gaps and/or an insulator which has very
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inversely proportional to the percent transmission for the yellow light which implied more photoelectrons were emitted for greater intensity. Stopping potentials for green light was noted to be higher than of yellow light. Ratio of Planck’s constant to electron charge and work function of the photocathode were determined experimentally from the plot of frequency vs. stopping potential from the first and second orders of spectral lines of mercury. The h/e ratio from the plot was 2.345 × 10-15 eV•s with 43
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Introduction: Electrons are negatively charged subatomic particles found in all atoms. Electrons have particle-wave duality‚ meaning they exhibit characteristics of particles‚ and characteristics of waves. A wave is a periodic function‚ meaning that the function returns to the same value at regular intervals. Also‚ waves have crests and troughs‚ meaning there are repeated local maxima (crests) and minima (troughs). Waves also have a wavelength and frequency. The wavelength is the distance in
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Since the birth of Physical Review Letters fifty years ago‚ condensed matter physics has seen considerable growth‚ and both the journal and the field have flourished during this period. In this essay‚ I begin with some general comments about condensed matter physics and then give some personal views on the conceptual development of the field and list some highlights. The focus is mostly on theoretical developments. DOI: 10.1103/PhysRevLett.101.250001 PACS numbers: 01.30.−y The transistor
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Explain the role of atomic number in MiniLab: Modeling Isotopes‚ p. 102 How Atoms Differ 2 sessions 1 block determining the identity of an atom. 6. Define an isotope and explain why atomic masses are not whole numbers. 7. Calculate the number of electrons‚ protons‚ and neutrons in an atom given its mass number and atomic number. Section 4.4 8. Explain the relationship between Careers Using Chemistry: Radiation Unstable Nuclei and Radioactive Decay 2 sessions 1 block unstable nuclei and radioactive
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small the radii of most atoms fall within the range of 5 x 10^-11 m to 2 x 10^-10m atoms can be seen in scanning electron microscopes atoms can be moved 4.2 Structure of the Nuclear Atom Overview Lots of Dalton’s theory is accepted except that atoms can be divided Atoms can be divided into three subatomic particles Protons Neutrons Electrons Subatomic Particles Electrons Discovered by UK physicist J.J. Thomson (1856-1940) Are negatively charged subatomic particles. Thomson’s Experiment
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large number of nearest neighbors(Why?). Properties of metals are largely defines by their electron structure. For sp-bonded metals assuming one can assume that the macroscopic properties are the energy of electron gas (see lecture notes of the fall semester). Energy of an electron gas with Fermi energy EF: 3 3 Nh 2 3π 2 N U = nEF = 5 10 m V ∂U P = − Pressure of electron gas: ∂V S ∂ 2U 2nEF ∂P = = −V B = −V Bulk modulus: ∂V 2
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Photoelectric effect Shining light on a metal causes electrons to be emitted Below some frequency‚ no photons are emitted regardless of intensity of light. As frequency of the light increases‚ the kinetic energy of the emitted electrons increase. As the intensity of the light increases under a certain frequency‚ the number of the electrons ( current I) increases. Photon energy is quantized. Some energy is needed to liberate an electron form a material. This amount of energy is called the
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1. a) Democritus reasoned that if matter could be infinitely divided‚ it was also subject to complete disintegration from which it can never be put back together. However‚ matter can be reintegrated. b) In Greek‚ the prefix "a" means "not" and the word "tomos" means cut. Our word atom therefore comes from atomos‚ a Greek word meaning uncuttable. All matter is composed of atoms‚ which are bits of matter too small to be seen. These atoms CANNOT be further split into smaller portions. 2. At
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Dispersion and the speed of light “So far as problems involving light are concerned‚ the electrons (in atoms) behave as though they were held by springs”.Feynman “In a microscopic but otherwise classical analysis‚ the electric field in electromagnetic radiation accelerates electrons held by springs in the atoms of a piece of glass‚ and these accelerated electrons re-radiate in all directions. The observed light is the superposition of the electric (and magnetic) fields of the incoming
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