Key relationship
ynet=yincident+yreflected; fixed-end reflection reverses sign, free-end reflection preserves sign.
Physics · Class 11
Overlap incident and reflected pulses
Where pulses overlap their displacements add algebraically. They then pass through with their original shapes in a linear medium. A pulse reflected at a fixed end inverts; a free-end reflection remains upright.
Open the interactive experiment →Overlap incident and reflected pulses
அலைகள் மேற்பொருந்தும்போது இடப்பெயர்ச்சிகள் இயற்கணிதமாக கூட்டப்படும். நிலையான முனையில் பிரதிபலித்த அலை தலைகீழாகும்.
Key notes, relationships and model limits
Remember
Where pulses overlap their displacements add algebraically. They then pass through with their original shapes in a linear medium. A pulse reflected at a fixed end inverts; a free-end reflection remains upright.
Common trap
Destructive interference during overlap does not erase the traveling pulses.
Model limits
Two ideal Gaussian pulses moving toward one another at 1 m/s; reflected sign chosen by boundary. This shows their post-reflection overlap, without resolving the actual end boundary or string tension dynamics.
What you will learn
Apply superposition and identify reflection phase changes.
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
At t=8 s, pulse centres both reach x=10 m. With A=0.5 m, fixed-end signs give 0.5−0.5=0; free-end signs give 0.5+0.5=1 m.
Why this matters
The model connects overlap incident and reflected pulses with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
Equal positive and negative pulses overlap exactly. What is net displacement?
- Twice either pulse amplitude
- Zero at that instant
- The two pulses permanently disappear
Read the explanation
The displacements cancel algebraically; the pulses are not permanently destroyed.
Course connection: Class XI Chapter 14. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.