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The wavelengths of the Kα X-ray lines for copper (atomic number 29) and molybdenum (atomic number 42) are denoted as λCu and λMo, respectively. What is the approximate value of the ratio λCu to λMo?

1. 1.99
2. 2.14
3. 0.50
4. 0.48

Correct answer: 2.14

Solution

The correct answer is 2.14 because the ratio of the wavelengths of the Kα X-ray lines for copper and molybdenum can be calculated using the formula λ2/λ1 = [Z1 − 1 / Z2 − 1]², where Z1 and Z2 are the atomic numbers of the elements.

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