They will cancel each other out... this even works with light and sound waves.
The result is destructive interference. The resultant displacement of the waves would be zero, but only for the moment of interference. Once the interference is past, the waves continue normally.
Constructive interference. The troughs will add and if your amplitude of either trough is a and b, the final trough will have amplitude a+b.
Wavelength.
From crest to crest, trough to trough or rest position to rest position
The wavelength of a wave is the distance between two identical parts of a wave in successive periods (crest to crest, trough to trough, etc.).
The result is destructive interference. The resultant displacement of the waves would be zero, but only for the moment of interference. Once the interference is past, the waves continue normally.
Constructive interference. The troughs will add and if your amplitude of either trough is a and b, the final trough will have amplitude a+b.
Wavelength.
From crest to crest, trough to trough or rest position to rest position
From crest to crest or trough to trough
From crest to crest or trough to trough
Is the wave length
wavelength
The wavelength of a wave is the distance between two identical parts of a wave in successive periods (crest to crest, trough to trough, etc.).
The distance from a crest to a crest or a trough to a trough in a wave.
Wavelength
I'm guessing you're talking about Transverse waves? eg. ~ Waves consist of two parts - a crest and a trough. The crest are the high points, and a trough is the low points. When a crest meets another crest, the wave is amplified, causing constructive interference (the crests add to each other). The same thing occurs when a trough meets a trough. However, when a crest meets a trough, the wave is diminished, causing destructive interference (the crest and trough cancel each other out).