Pitch Change with Temperature – Rankers Physics

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.  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Short Solution (Best for NEET):

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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