Question 13 Marks
Prove that the pitch of a wind instrument depends on the length of the vibrating air column.
Answer
View full question & answer→The following activity shows that the pitch of a wind instrument depends on the length of the vibrating column.
Materials required : Four test tubes, a beaker containing water and a test tube holder.
Procedure : Place the test tubes in the test tube holder and label them as $A, B, C$ and $D$ from left to right. Fill the test tubes with water such that the level of water rises as you go from $A$ to $D$. This means that the length of air column decreases as we move from $A$ to $D$. Blow air in the test tube a by putting your lips over its mouth. Now, repeat the procedure with the test tubes $B, C$ and $D$.
Observation : The sound produced by test tubes becomes shriller as we move from $A$ to $D$. In other words, the pitch of the sound produced by the test tubes when air is blown over their mouths increases as we move from $A$ to $D$.
Conclusion : The pitch of the vibrating air column increases with the decrease in the length of air column.
Materials required : Four test tubes, a beaker containing water and a test tube holder.
Procedure : Place the test tubes in the test tube holder and label them as $A, B, C$ and $D$ from left to right. Fill the test tubes with water such that the level of water rises as you go from $A$ to $D$. This means that the length of air column decreases as we move from $A$ to $D$. Blow air in the test tube a by putting your lips over its mouth. Now, repeat the procedure with the test tubes $B, C$ and $D$.
Observation : The sound produced by test tubes becomes shriller as we move from $A$ to $D$. In other words, the pitch of the sound produced by the test tubes when air is blown over their mouths increases as we move from $A$ to $D$.
Conclusion : The pitch of the vibrating air column increases with the decrease in the length of air column.