Determining Diet. One method for determining the amount of corn in early
Native American diets is the stable isotope ratio analysis (SIRA) technique.
As corn photosynthesizes, it
concentrates the isotope carbon-13, whereas most other plants concentrate
carbon-12. Overreliance on corn consumption can then be
correlated with certain diseases, because corn lacks the essential amino acid
lysine. Archaeologists use a mass spectrometer to separate the 12\(\mathrm { C
}\) and \(^ { 13 } \mathrm { C }\) isotopes in samples of human remains. Suppose
you use a velocity selector to obtain singly ionized (missing
one electron) atoms of speed \(8.50 \mathrm { km } / \mathrm { s } ,\) and you
want to bend
them within a uniform magnetic field in a semicircle of diameter 25.0\(\mathrm
{ cm }\) for the 12\(\mathrm { C }\) . The measured masses of these isotopes are
\(1.99 \times 10 ^ { - 26 } \mathrm { kg } \left( ^ { 12 } \mathrm { C }
\right)\) and \(2.16 \times 10 ^ { - 26 } \mathrm { kg } \left( ^ { 13 } \mathrm
{ C } \right) .\) (a) What strength of magnetic field is required? (b) What is
the diameter of
the 13 C semicircle? (c) What is the separation of the \(^ { 12 } \mathrm { C
}\) and \(^ { 13 } \mathrm { C }\)
ions at the detector at the end of the semicircle? Is this distance
large enough to be easily observed?