Here's my guitar - as seen at Rock Night on Friday! Waves on the sea are called PROGRESSIVE WAVES because the peak (the crest of the wave) moves forward as time goes by. On a guitar, the peak stays in the same place but just goes up and down. The ends of the string are fixed so provided that the wavelength fits in perfectly, you get what is called a STATIONARY WAVE.
The conditions necessary to make a stationary waves are :
- Two waves travelling in opposite directions
- With the same frequency
- With the same speed
- With the same amplitude.
Here, the wave travelling in the opposite direction is made by the first wave reflecting back from ne of the fixed ends.
Players of stringed instruments will know that it is possible to play what are known as harmonics. Here, I gently placed one finger half way down the string to force that part of the string to be still (it's called a NODE). Then I plucked the string. The note was twice as high as the open string, with two vibrating sections. Technically, this second wave represents a full wavelength because a full wavelength has both a peak and a trough. The open string is only half a wavelength.
