Finding ratio of wavelengths

1. May 4, 2015

Raghav Gupta

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 λCuMo 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?

2. May 4, 2015

BvU

There is some other formula. I google "k-alpha x-ray energy"and wikipedia tells me the answer straight away. You can do that too !

3. May 4, 2015

Raghav Gupta

Oh, so that is Moseley's formula. Never seen that.
It was formula oriented , okay.