Sound Wave and its Characteristics: Practice Problem & Solution
Assertion (A): The pitch of wind instruments rises and that of string instruments falls as an orchestra warms up. Reason (R): When temperature rises, speed of sound in air increases but speed of wave in a string fixed at both ends decreases.
Solution Explained:
To solve this problem, we apply the core principles of Sound Wave and its Characteristics. Understanding the underlying formula is key to arriving at the correct answer below:
For wind instruments, pitch \( f \) is proportional to the speed of sound in air \( v_{\text{air}} propto \sqrt{T_{\text{temp}}} \). As temperature rises, \( v_{\text{air}} \) increases, so pitch rises. For string instruments, \( f propto v_{\text{string}} = \sqrt{T_{\text{tension}}/\mu} \). As temperature rises, the string expands, reducing tension \( T_{\text{tension}} \), so \( v_{\text{string}} \) decreases and pitch falls. Reason R accurately explains this behavior for both cases.
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