This week's questions test whether you understand the hydrogen energy level diagram and also the new reading from Universe, section 19(5) and also box 7-2

    1.  In class today we showed how visible, ultraviolet, and infrared light could be produced by certain transitions in the hydrogen atom's energy level diagram. 

a) Can the neutral hydrogen atom emit spectral lines at x-ray wavelengths?  If so, convince me how (perhaps by presenting a sample transition).  If not, be convincing as to why not.

b) Can the neutral hydrogen atom emit spectral lines at radio wavelengths?  If so, convince me how (perhaps by presenting a sample transition).  If not, be convincing as to why not.

   2. a) If you look at the spectra of stars in the text [section 19(5)], you see that the Balmer lines of neutral hydrogen are the darkest (or strongest) in stars labeled spectral class A.  In order for the Balmer lines to be dark/strong, in what level(s) must the hydrogen electron have been in these type A stars in order to produce these lines? 

b) on the other hand, where (i.e., in what level) would you suspect that the hydrogen electrons to be in stars that are cooler in temperature than spectral class A (which would explain why they CANNOT produce the Balmer series of lines in absorption)?

   3. Now that we have beat hydrogen to death (nearly), we need to address all the other atoms in short order....  let's try helium... (the first two questions below are a quick test of whether you can read properly the ionization chart in the blue book; the third question's answer can be found in the reading)

a) how much energy is required to remove just one electron from neutral helium?

b) how much energy is required (starting with neutral helium) to remove all the electrons from neutral helium?

c) why is it more likely that the helium (or anything else, for that matter) will be ionized in hotter stars than in cooler stars? (there are two reasons!)