Yes. An electromagnetic wave follows a sine-wave pattern.
Crest and trough Image commons.wikimedia.org/wiki/File:Crest_trough.svg
which kind of sound is produced by sound waves with peaks that are very close together?
Coherent
As all EM waves do a constant speed ('c'). If the frequency increases (i.e. the waves are more frequent) the distance between the wave peaks (wavelength) must reduce. For visible light waves, this produces a 'blue shift.'
Peaks and valleys to not create water waves, they are characteristic elements of water waves.
Sound Waves
Yes. An electromagnetic wave follows a sine-wave pattern.
Crest and trough Image commons.wikimedia.org/wiki/File:Crest_trough.svg
All of them. Electromagnetic, sound, even a water wave until it hits shore.
When waves of the same frequency are in phase they reinforce each other when their peaks and valleys occur at the same point. They add up.
CHiPs - 1977 Peaks and Valleys 2-1 was released on: USA: 16 September 1978
old
It depends which country or region you are talking about.
which kind of sound is produced by sound waves with peaks that are very close together?
If you have two waves, or two things in oscillation or two things in vibration; if the peaks (maximum amplitude) and valleys (maximum amplitude the other way) occur at the same time then they are in phase. If one wave peaks at the same time the other one is in a valley they are said to be 180 degrees out of phase.
young