Tuesday, 24 January 2017

More about waves

Imagine the guitar string we plucked in the middle in an earlier post. it vibrates from side to side. The amplitude, or size of the vibration is widest at the middle and tails off towards the end of a string.
Now, if you place your finger lightly at the middle of a guitar string, and pluck it gently about three quarters of the way along it, you will find a completely different pattern of vibration. Now the middle of the string doesn't move at all. Instead the two halves of the string vibrate. The size of  the vibration is biggest at the mid-points of the two halves of the string.  We probably need a picture to explain this clearly, so I've added one below. If you are careful you can make the guitar string vibrate in three or even four separate sections.
The picture below shows a string vibrating in four separate ways. Each has one more vibrating segment than the one above it.

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