Physics Chapter 21 Atomic Physics Conceptual Questions

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Why is the term ultraviolet catastrophe used to describe the discrepancy between the predictions of classical physics and the experimental data for blackbody radiation?
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Because the discrepancy happens at the ultraviolet end of the spectrum (Drastic change)
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What is meant by the term quantum?
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A discrete quantity
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What did Planck assume in order to explain the experimental data for blackbody radiation? How did Planck’s assumption contradict classical physics?
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Energy radiated by a black body is quantized, while classical physics says energy is continuous
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What is the relationship between a joule and an electron volt?
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1ev= 1.6×10^-19 J
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How do observations of the photoelectric effect conflict with the predictions of classical physics?
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Frequency or color rather than intensity determines whether or not electrons are ejected. KEmax depends on frequency not intensity
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Which has more energy, a photon of ultraviolet radiation or a photon of yellow light?
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A photon of ultraviolet radiation
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If the photoelectric effect is observed for one metal using light of a certain wavelength, can you conclude that the effect will also be observed for another metal under the same conditions?
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No, because different metals have different work functions
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what effect, if any, would you expect the temperature of a material to have on the ease with which electrons can be ejected from the metal in the photoelectric effect?
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The hotter the temperature, the more excited the electrons are, and they are easier ejected
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What did Rutherford’s foil experiment reveal?
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Charge and mass are concentrated at the atom’s center
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If Rutherford’s planetary model were correct, atoms would be extremely unstable. Explain why?
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Because orbiting electrons would radiate energy The electron will crash into the nucleus
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How can the absorption spectrum of a gas be used to identify the gas?
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Each gas has a unique emission spectrum
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What restriction does the Bohr model place on the movement of an electron in an atom?
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The electron is limited to seven orbits
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How is Bohr’s model of hydrogen similar to Rutherford’s planetary model? How are the two models different?
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The electron orbits the nucleus in both models, however in Ruthorford’s model, any orbits are possible, but in Bohr’s model only certain orbits are allowed
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How does Bohr’s model account for the atomic spectra?
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Spectral lines correspond to jumps between stable orbits
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what is another word for quantum of light?
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D photon
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According to classical physics, when a light illuminates a photosensitive surface, what should determine how long it takes before electrons are ejected from the surface?
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G Intesnity
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According to Einstein’s photo theory of light, what does the intensity of light shining on a metal determine?
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A The number of photons hitting the metal in a given time interval
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An X-ray photon is scattered by a stationary electron. How does the frequency of this scattered photon compare to its frequency before scattered?
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G The frequency is lower
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Which of the following summarizes Thomson’s model of the atom?
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B Electrons are embedded in a sphere of positive charge
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What type of spectrum is created by applying a high potential difference to a pure atomic gas?
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an emission specturm
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What type of spectrum is used to identify elements in the atmospheres of stars?
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an absorbtion specturm
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What does Heisenberg’s uncertainty principal state?
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it is impossible to simultaneously measure a particle’s position and momentum with infinite accuracy
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How do de Brogile’s matter waves account for the “allowed” electron orbit
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Allowed orbits are those that contain N number of orbits
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Why can the wave properties of an electron be observed, while those do a speeding car cannot
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If the velocity is small, the wavelength is larger. In order for the speeding car to be observed, the velocity of the car would need to be way to big to be plausible.
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Discuss why the term electron cloud is used to describe the arrangement of electrons in the quantum-mechanical view of the atom
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Because the electrons location cannot be determined exactly
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An electron and a photon are accelerated from rest through the same potential difference. Which particle has the longer wavelength?
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The electron because it has the smaller mass and it can move faster
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What happens when an election moves from a higher energy level to a lower energy level in an atom?
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J A photon is emitted with energy equal to the difference in energy between two levels
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identify the behavior of an electron as primarily like a wave or a particle when it is traversing a circular orbit in a magnetic field
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particle
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identify the behavior of an electron as primarily like a wave or a particle when it is absorbs a photon and being ejected from the surface of the metal
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particle
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identify the behavior of an electron as primarily like a wave or a particle when it is forming an interference pattern
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wave
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Describe Bohr’s model of the atom. Identify the assumptions that Bohr made that were a departure from those of classical physics. Explain how Bohr’s model accounts for atomic spectra.
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the electrons only orbit the nucleus only in desecrate energy levels. The model departs from classical physics in that the electrons are only allowed to have certain energies

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