Atoms

A metal target with atomic number Z = 46 is bombarded with a high energy electron beam. The emission of X-rays from the target is analyzed. The ratio r of the wavelengths of the K -line and the cut-off is found to be r = 2. If the same electron beam bombards another metal target with Z = 41, the value of r will be

1. 2.53
2. 1.27
3. 2.24
4. 1.58