Two identical light waves, A and B, are emitted from different sources and meet at point P. The distance from the source of A to point P is
L_{A}. The distance from the source of B to point P is
L_{B}. Which of the following statements is necessarily true concerning the interference of the two waves?
- A and B will interfere constructively because their amplitudes are the same.
- A and B will interfere constructively if L_{A}= L_{B}
- A and B will interfere destructively if L_{A}-L_{B}=mλ where m=0,1,2,3,...
- A and B will interfere destructively if L_{A} is not equal to L_{B}
- A and B will interfere constructively because their wavelengths are the same.