Question:
In radiometric surveys, potassium in subsurface rocks will show a $\gamma$-ray peak in which one of the following MeV energy channels?
In radiometric surveys, potassium in subsurface rocks will show a $\gamma$-ray peak in which one of the following MeV energy channels?
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In gamma-ray spectrometry, always remember: Potassium shows a peak at 1.46 MeV, Uranium at 1.76 MeV, and Thorium at 2.62 MeV.
Updated On: Aug 22, 2025
- 0.92
- 1.46
- 1.76
- 2.62
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The Correct Option is B
Solution and Explanation
Step 1: Understanding the radioactive isotope of potassium.
Potassium ($K$) in rocks is mostly $^{40}$K, which is a naturally occurring radioactive isotope. It undergoes radioactive decay by: - $\beta^-$ decay (to $^{40}$Ca), and - electron capture (to $^{40}$Ar). Step 2: Gamma-ray emission.
During the electron capture decay of $^{40}$K to $^{40}$Ar, a characteristic gamma-ray photon is emitted. The energy of this $\gamma$-ray photon is 1.46 MeV. Step 3: Radiometric survey application.
In radiometric surveys, different isotopes are identified by their characteristic gamma-ray energy peaks: - $^{40}$K : 1.46 MeV
- $^{214}$Bi (Uranium series): 1.76 MeV
- $^{208}$Tl (Thorium series): 2.62 MeV Thus, the peak for potassium is uniquely observed at 1.46 MeV. \[ \boxed{1.46 \, \text{MeV}} \]
Potassium ($K$) in rocks is mostly $^{40}$K, which is a naturally occurring radioactive isotope. It undergoes radioactive decay by: - $\beta^-$ decay (to $^{40}$Ca), and - electron capture (to $^{40}$Ar). Step 2: Gamma-ray emission.
During the electron capture decay of $^{40}$K to $^{40}$Ar, a characteristic gamma-ray photon is emitted. The energy of this $\gamma$-ray photon is 1.46 MeV. Step 3: Radiometric survey application.
In radiometric surveys, different isotopes are identified by their characteristic gamma-ray energy peaks: - $^{40}$K : 1.46 MeV
- $^{214}$Bi (Uranium series): 1.76 MeV
- $^{208}$Tl (Thorium series): 2.62 MeV Thus, the peak for potassium is uniquely observed at 1.46 MeV. \[ \boxed{1.46 \, \text{MeV}} \]
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