Key relationship
λmin=hc/(eV); simplified Kα energy≈(3/4)13.606(Z−1)² eV.
Physics · Class 12
X-ray continuum and target lines
The maximum electron energy sets the short-wavelength cutoff. Target atomic number sets characteristic transitions. Raising tube voltage moves the cutoff without shifting a given target line, once excitation is possible.
Open the interactive experiment →X-ray continuum and target lines
குழாய் மின்னழுத்தம் குறைந்தபட்ச அலைநீளத்தை நிர்ணயிக்கும். இலக்கு அணு எண் அதன் தனிப்பட்ட எக்ஸ் கதிர் வரிகளை நிர்ணயிக்கும்.
Key notes, relationships and model limits
Remember
The maximum electron energy sets the short-wavelength cutoff. Target atomic number sets characteristic transitions. Raising tube voltage moves the cutoff without shifting a given target line, once excitation is possible.
Common trap
The plotted envelope is illustrative; it is not a measured X-ray spectrum.
Model limits
Ideal electron tube; continuum graph is a normalized schematic envelope. Kα uses a screened hydrogenic Z−1 estimate, not precision target spectroscopy. K-shell threshold approximated consistently.
What you will learn
Separate continuum cutoff from characteristic lines.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
40 kV gives λmin≈0.0310 nm; the Z29 estimate gives Kα≈0.155 nm.
Why this matters
The model connects x-ray continuum and target lines with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
Doubling tube voltage changes λmin to?
- Twice
- Half
- Unchanged
Read the explanation
λmin is inversely proportional to voltage.
Course connection: Class XII Chapter 12. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.