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Chapter 44: Quarks, Leptons, and the Big Bang

Fundamentals Of Physics
Pages: 1334 - 1368

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63 Questions for Chapter 44: Quarks, Leptons, and the Big Bang

  1. Question: Due to the presence everywhere of the cosmic background radiation, the minimum possible temperature of a gas in interstellar or intergalactic space is not 0 K but 2.7 K. This implies that a significant fraction of the molecules in space that can be in a low-level excited state may, in fact, be so. Subsequent de-excitation would lead to the emission of radiation that could be detected. Consider a (hypothetical) molecule with just one possible excited state. (a) What would the excitation energy have to be for 25% of the molecules to be in the excited state? (Hint: See Eq. 40-29.) (b) What would be the wavelength of the photon emitted in a transition back to the ground state?

    Found on Page 1365
  2. Question: Figure 44-12 is a hypothetical plot of the recessional speeds v of galaxies against their distance r from us; the best-fit straight line through the data points is shown. From this plot determine the age of the universe, assuming that Hubble’s law holds, and that Hubble’s constant has always had the same value

    Found on Page 1365
  3. Question:How much energy would be released if Earth were annihilated by collision with an anti-Earth?

    Found on Page 1365
  4. A neutral pion has a rest energy of 135 MeV and a mean life of8.3×10-17s . If it is produced with an initial kinetic energy of 80 MeV and decays after one mean lifetime, what is the longest possible track this particle could leave in a bubble chamber? Use relativistic time dilation.

    Found on Page 1363
  5. As we have seen, the π-1meson has the quark structure du¯.

    Found on Page 1362
  6. Which conservation law is violated in each of these proposed decays? Assume that the initial particle is stationary and the decay products have zero orbital angular momentum.

    Found on Page 1363
  7. Consider the neutrino whose symbol is ντ¯ . (a) Is it a quark, a

    Found on Page 1363
  8. The A2+ particle and its products decay according to the scheme

    Found on Page 1363
  9. Show that if, instead of plotting strangenessS versus chargeq for the spin -12baryons in Fig. 44-3a and the spin-zero mesons in Fig.44-3b , we plot the quantity Y=B+Sversus the quantity Tz=q-12(B+S), we get the hexagonal patterns without using sloping axes. (The quantityY is called hypercharge, andTzis related to a quantity called isospin.)

    Found on Page 1363
  10. Calculate the disintegration energy of the reactions

    Found on Page 1364

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