Question

There are two bottles of glass, one bottle is two third filled with water and another bottle is filled one third with water. When we blow across the mouth of each bottle, then
(i) The bottle with the less air in it gives the note of higher pitch.
(ii) The shorter the air column, the higher the pitch of the note produced.

Answer 1

If the length of the vibrating body increases, the frequency of vibration decreases.
If the length of the vibrating body decreases, the frequency of vibration increases.
If a bottle is filled with water, the remaining part acts as air column. If we blow across the mouth of bottle, the air column will vibrate and produce sound.
The air column in case of bottle with one third of water is more than that of the bottle with two third of water. Hence, the sound produced in case of bottle with two third of water in it will produce note of higher pitch.
The statement (ii) is correct as it tells that the shorter the air column, the higher the pitch of the note produced. Also the statement (ii) is the correct explanation of statement (i).