H   Chapter 18 - Superposition
H   Particles and waves have different characteristics. Particles have 'zero' size. While waves have infinite extent. Particles cannot be in the same place at once. Two or more waves can be at the same location! This will lead to fantastic results.    
If two or more traveling waves are moving thru a medium, the resultant value of the wave function at any point is the algebraic sum of the values of the wave functions of the individual waves.
Animation courtesy of Dr. Dan Russell, Kettering University.
    When adding waves

When the waves are 180° out of phase

the waves destructively interfere

When the waves are in phase
the waves contructively interfere
courtesy of:http://www.calvin.edu/academic/phys/
Real World Interference

same frequency, same wavelength, different phase
Path Difference
Adding Waves
point by point

      Signal Cancellation