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Unformatted text preview: ws of atoms. Each
row made of 100 atoms, separated from on another by 0.2 nanometers. The molecule is then
made of many of these atom rows. In it, the rows are tilted 25 from the horizontal (see below)
and spaced 10 nm apart. These molecules are illuminated by X-rays with a wavelength of 0.1
nm. Which of the following could be the diffraction pattern observed in this experiment? Circle
your choice. 25 10 nm 14: (5 points) Two sources of sound waves oscillate at a frequency of 2000 Hz, exactly out of
synch with one another; when the first source is producing a maximum, the second is producing
a minimum. They are located 34 cm apart. Consider a point C located above the midpoint
between the sources. At what position y do the two sources interfere constructively?
e) 12.5 cm
34 cm 15: The isotope 146C decays via beta decay to 147N. This carbon isotope has a mass of
14.003241 amu, while the nitrogen isotope has a mass of 14.003074 amu. Remember that 1
amu = 1.67x10-27 kg. In this decay does the binding energy per nucleon (2 points):
And by what amount (3 points)?
e) 0.16 MeV / nucleon
0.011 MeV / nucleon
1.42 MeV / nucleon
0.43 MeV / nucleon
0.93 MeV / nucleon 16: (5 points) Consider the following small piece of the periodic table. Remember that this table
shows you only the most common stable isotopes. The isotope 137N is radioactive, with a halflife of around 9 minutes. What isotope would you expect 137N to decay into? Explain your
6C 17: (5 points) Plane waves of light with a wavelength of 500 nm are incident on a circular hole
in an opaque screen. The diameter of this hole is 1500 nm. The diffraction pattern from such a
hole looks like this: Would you expect the first minimum in this pattern to appear at an angle such that:
a) sinmin = 1/3
b) sinmin > 1/3
c) sinmin < 1/3
Explain your answer briefly. 18: (5 points) The typical annual dose of radiation received from your surroundings is about 0.1
REM. If this radiation were received mostly in the form of gamma-rays (with RBE = 0.6), and
you weigh 70 kg, what total amount of energy might you expect to receive during the two hours
of this exam?
e) 2.7x10-3 J / exam
0.167 J / exam
5.2 J / exam
8.4 J / exam
11.7 J / exam 19: (5 points) Consider the following graph showing the relative abundance of different elements
in the solar system. Explain why gold (Au, atomic number 79) is so much less abundant than helium (He). Be sure,
in your discussion, to discuss when and how each was formed. 20: (5 points) Describe briefly two reasons why the detection of Earth sized planets by transit
measurements is so difficult. 1: 2:...
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- Spring '08