At what point do the weak nuclear and electromagnetic forces split?
A) never, they are still united
B) at 1012 K, when pair production starts for neutrons and protons
C) at 10-43 seconds, when all four forces separate as the Planck Era ends
D) at about four seconds, when at millions of degrees hydrogen forms helium
E) after about 10-10 seconds, when the temperature drops below 10-15 K
E
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Light of wavelength 633 nm from a He-Ne laser passes through a circular aperture and is observed on a screen 4.0 m behind the aperture. The diameter of the central bright area is 5.4 cm. What is the diameter of the aperture?
A) 2.0 ?m B) 960 ?m C) 110 ?m D) 6600 ?m
Energy Levels: What is the ground state energy of the Li++ ion, which has atomic number 3?
A. -40.8 eV B. -122 eV C. -61 eV D. -1.51 eV E. Li++ does not have a ground state.
Escape Speed: Planet A has twice the mass of Planet B. From this information, what can we conclude about the escape speed for Planet A compared to that of Planet B?
A. The escape speed for Planet A must be twice as great as the escape speed from Planet B. B. The escape speed for Planet A must be four times as great as the escape speed from Planet B. C. The escape speed for Planet A is the same as the escape speed from Planet B. D. The escape speed for Planet A is greater than the escape speed from Planet B, but we cannot say how much greater. E. We cannot conclude anything about the escape speed for Planet A without knowing the radii of the two planets.