Calculate X-Ray Wavelength for Lead Target

[conniechiwa]

Homework Statement

The tube in a medical research X-ray unit uses lead (Z=82) as it's target. Assume the electrons are accelerated through the voltage calculated in part (b). What is the wavelength of the Kα line?

Homework Equations

KE=-13.6 ev ((Z-1)squared) / (1squared)
KE=PE=VQ
E=QV
λ=hc/E

The Attempt at a Solution

KE=-13.6 ev ((Z-1)squared) / (1squared)
KE =-13.6 ev ((82-1)squared)/ 1 squared)
KE=89229.6 ev

KE=PE=QV
89229.6=(1.602E-19 J/ev)V
V=89229.6 V

E=QV
E=(1.602E-19 C)(89229.6V)
E=1.429E-14 J

λ=hc/E
λ=((6.63E-34 J*s)(3E8 m/s))/(1.429E-14 J)
λ=1.3856E-11 m = 0.013856 nm

I'm not sure what's wrong... I correctly solved for KE and V, but I can't seem to solve for λ.

 

[Astronuc]

I'm not sure where part b is, but think about the energies.

The accelerated electron must have enough energy to dislodge a K-electron from the lead atom.

Then another orbital electron will fall from a higher state to the spot in the K-shell, so the X-ray energy represents a difference in energy levels of atomic electrons. What's the significance of Kα?

 

[conniechiwa]

Oh okay I got it now. Thanks!