Davisson and Germer used a nickel crystal for their scattering experiments that had been modified when they tried to repair it. Which of the following describes the major change from before they tried to repair it and afterward that allowed them to work on the groundbreaking experiments they did?

A. The oxidation of the nickel from immediately after it was taken from a vacuum environment introduced impurities with intermediate band gaps.
B. The heating processes created larger crystals, which allowed them to clearly see the electron diffraction.
C. Under the intense heat of their repair process, the electrons were scattered off of energetically oscillating nickel atoms, whereas before they hit the stationary lattice atoms.
D. Their knowledge of the new nickel crystals led them to believe that electrons with low energy (on the order of ~10 eV) only would scatter off of the closely spaced nickel atoms.

B.
The larger crystals that formed were more orderly than the fewer small crystals previously in the nickel structure. This allowed Davisson and Germer to clearly see the electron scattering patterns inherent to the large crystals.

Physics & Space Science

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Aluminum-lithium alloys were developed for aircraft applications because of their relatively high yield strength and low _________.

Fill in the blank(s) with the appropriate word(s).

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Iron atoms have a greater tendency to oxidize than do copper atoms. Is this good news or bad news for a home in which much of the plumbing consists of iron and copper pipes connected together? Explain

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A. 197 nm B. 167 nm C. 216 nm D. 234 nm

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A tank holds a 1.44-m thick layer of oil that floats on a 0.96-m thick layer of brine. Both liquids are clear and do not intermix. Point O is at the bottom of the tank, on a vertical axis

The indices of refraction of the oil and the brine are 1.40 and 1.52, respectively. A ray originating at O crosses the brine-oil interface at a point 0.60 m from the axis. The ray continues and emerges into the air above the oil. What is the angle that the ray in the air makes with the vertical? A) 48° B) 51° C) 54° D) 57° E) 60°

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