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### Chapter 1, Question 1.23

Posted: Tue Oct 10, 2017 5:38 pm
Q 1.23 “The y-ray photons emitted by the nuclear decay of a technetium-99 atom used in radiopharmaceuticals have an energy of 140.511 keV. Calculate the wavelength of these y-rays.”

I‘m not sure how to begin this problem. What measurement is keV exactly, and how do you convert it to joules?

### Re: Chapter 1, Question 1.23

Posted: Tue Oct 10, 2017 9:52 pm
1keV = 1000 ev
1 ev = 1.6*10^-19 Joules. Electron-volts are just different units for energy.

### Re: Chapter 1, Question 1.23

Posted: Tue Oct 10, 2017 10:01 pm
In addition to converting keV to Joules, another way to start this problem is to use the equation:

wavelength = (hc)/E

h and c are both constants, so we only need to plug in our value for energy for Joules to start the problem. Hope this helps!

### Re: Chapter 1, Question 1.23

Posted: Wed Oct 11, 2017 10:20 am
First, you must convert 140.511 eV to Joules. (1eV = 1.6022 x 10^-19 J).

From there, you use the equation E=hc/lambda and solve for lambda (wavelength).