Question

Making music:

If you have a series of identical glass bottles, with varying amounts of water in them, you can play musical notes by either striking the bottles with a spoon or blowing across the open tops of the bottles. When you change the water levels in the bottles, you will get a different change in the frequency of the note produced depending on which of the two methods you use to produce it. Discuss the following two cases in detail.

a) When hitting the bottle, the frequency of the note decreases as the water level rises. Why?

b) When blowing on the bottles, the frequency of the note increases as the water level rises. Why?

Answer 1

a )

when hits the bottle the sound will produced by vibrating the Glass particle.

and freuency of a note depends on resonance frequency of glass.

when water level increased mass to vibrate is increased, then the note of the frequency is getting decreases.

b )

the glass bottle will looks like a one end is closed and the other end open.

the resosnance frequency is f = n V / 2 L

as water level rises the length of the vibrating column decreases.

then the frequency of note is increases.