The ratio of the energies of the K characteristic X-rays of carbon (Z = 6) to those of magnesium (Z = 12) is most nearly
A. 1/4
B. 1/2
C. 1
D. 2
E. 4
(GR9277 #03)
Solution:Moseley’s law:
K-series refers to a transition from some outer state, ni to the inner-most shell, nf = 1.
(The order from inner to outer → K, L, M, N).
→ E ≈ (Z − 1)2
Ecarbon = (6 − 1)2 = 25
Emagnesium = (12 − 1)2 = 121
The ratio = 25/121 ≈ 1/4
Answer: A
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