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Chapter 34: Q13CQ (page 1237)
Does observed gravitational lensing correspond to a converging or diverging lens? Explain briefly.
Gravitational lensing corresponds to a converging lens.
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If neutrino oscillations do occur, will they violate conservation of the various lepton family numbers (\({{\rm{L}}_{\rm{e}}}\),\({{\rm{L}}_{\rm{\mu }}}\), and \({{\rm{L}}_{\rm{T}}}\))? Will neutrino oscillations violate conservation of the total number of leptons?
Suppose you measure the red shifts of all the images produced by gravitational lensing, such as in figure below. You find that the central image has a red shift less than the outer images, and those all have the same red shift. Discuss how this not only shows that the images are of the same object, but also implies that the red shift is not affected by taking different paths through space. Does it imply that cosmological red shifts are not caused by traveling through space (light getting tired, perhaps)?
Distances to local galaxies are determined by measuring the brightness of stars, called Cepheid variables, that can be observed individually and that have absolute brightness at a standard distance that are well known. Explain how the measured brightness would vary with distance as compared with the absolute brightness.
Assume the average density of the universe is\({\rm{0}}{\rm{.1}}\)of the critical density needed for closure. What is the average number of protons per cubic meter, assuming the universe is composed mostly of hydrogen?
How does relativistic time dilation prohibit neutrino oscillations if they are massless?
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