Astronomy 110G-05:   Final Exam (Sample)
SHORT QUESTIONS       (15 × 5 = 75 points)
Please keep your answers brief, and to the point. For multiple choice questions, chose and circle one and only one answer.

Draw an atom of neutral helium in an excited state below (we have started the sketch for you). Add an arrow showing what happens when the atom emits a photon.

Sketch of an atom. The atom is represented by a small circle (the nucleus), with three larger circles surrounding it. The final two circles (those furthest from the nucleus) are closest to each other.

Sort the following in order of increasing energy: infrared, optical, radio, ultraviolet and x-ray radiation.
      [a] ultraviolet, x-ray, radio, infrared, optical
      [b] radio, optical, ultraviolet, infrared, x-ray
      [c] radio, infrared, optical, ultraviolet, x-ray
      [d] infrared, ultraviolet, x-ray, radio, optical

Which is faster, the speed of light or the speed of sound?



Which is heavier, the nucleus of a hydrogen atom or the nucleus of a helium atom?



Is thermonuclear fission the primary source of the Sun's energy? Why, or why not?



Sketch a continuum spectrum, an absorption spectrum, and an emission spectrum.








For each of the three spectrum, name an object that gives off light in this form.
      [continuum]
      [absorption]
      [emission]

What is the difference between the progenitor (the star from which it forms) of a white dwarf and a neutron star?





What substance will a white dwarf star be made up of, at the end of its lifetime?

What is the true nature of the spiral nebulae, debated by Shapley and Curtis in 1920?





What role did Cepheid variable stars play in their arguments?




If we found a nearby black hole and sent a scientific probe into it, could the probe send back information to us on the contents of the central singularity? Why, or why not?





What are the three primary components of a spiral galaxy?





THE BLACKBODY AND ENERGY RELATIONS       (5 × 5 = 25 points)
Please draw a box around your final answer for each question. We will give partial credit, so show your work and attempt every question.

The surface temperature of Pluto is 50 K. The surface of Pluto is thus
      [a] colder than the surface of Venus.
      [b] the same temperature as the surface of Venus.
      [c] hotter than the surface of Venus.

What is the primary reason for this?




What is the wavelength, l, at which Pluto radiates the most energy?





Recall that we can define the amount of energy in light by either its wavelength, l, or its frequency, v, and that the speed of light is 3 × 105 kilometers per second. What is the frequency at which Pluto radiates the most energy?

Light of this wavelength and frequency has:
      [a] a shorter wavelength and higher frequency than optical light.
      [b] a shorter wavelength and lower frequency than optical light.
      [c] the same wavelength and frequency as optical light.
      [d] a longer wavelength and higher frequency than optical light.
      [e] a longer wavelength and lower frequency than optical light.

Extra credit: What is the name for this portion of the electromagnetic spectrum?