The short-wavelength limit shifts by 26 pm when the operating voltage in an X-ray tube is increased to 1.5 times the original value. What was the original value of the operating voltage?

Explanation

`(hc)/lambda=eV`
`lambda prop 1/V`
`lambda_(1)/lambda_(2)=V_(2)/V_(1)`
`lambda/(lambda-26)=(1.5 V)/V`
`lambda=1.5 lambda-1.5xx26`
`lambda=78 p m=0.078 nm`
`E(eV)=1242/(lambda(nm))=1242/0.078=15.9xx10^(3) eV`
`eV_(1)=15.9 ke V`
`V_(1)=15.9 kV`