Answer:
a crest and a trough meeting
Explanation:
Interference is a phenomenon which occurs when two or more waves come together. Each wave will have a crest (positive amplitude) and a trough (negative amplitude).
If the magnitude of resultant wave’s amplitude is smaller than the original waves, then there is a destructive interference.
It happens if the path difference is integral multiples of half wavelength
Δφ = n (λ/2)
In this case amplitudes of the original waves will have opposite signs.
Since crests have positive amplitude and troughs have negative amplitude they will create a destructive interference
If the magnitude of resultant wave’s amplitude is larger than the original waves, then there is a constructive interference.
It happens if the path difference is integral multiples of the wavelength
Δφ = nλ
In this case amplitudes of the original waves will have same signs.
