1. The problem statement, all variables and given/known data If λCu is the wavelength of Kα X-ray line of copper (atomic number 29) and λMo is the wavelength of the KαX-Ray line of molybdenum (atomic number 42), then the ratio λCu/λMo is close to 1.99 2.14 0.50 0.48 2. Relevant equations De broglie relation λ = h/p 3. The attempt at a solution How to calculate momentum? Or is there some other formula?