Answer: In double slit case, you need to understand superposition on waves emerging from dirrerent slit.
Explanation: When passing a single slit, wave spread in all directions.
In double slit waves with equal wavelength travel different path and distance
trey travel is different . Waves meet each other in different positions in different phases. If phase are same, waves have contructive interference, crests of waves meet in same point. Amplitudes of waves are added together. If waves are in opposite phases, sum of amplitudes
ame subtacted and this is destructive interference. Sum of amplitudes are zero.
