1. The problem statement, all variables and given/known data i read some online notes. from there , i know that if the beat frequnecy ( difference in frequncies between 2 waves ) is low , then the time taken for two waves to be in phase again is very long.... which means more number of waves has to be produced for two waves to be in phase again. Period of beat = 1/(f1-f2) ....Why is it so ? can someone explain in a 'physics way' ?