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Question:

A musical instrument is made using four different metal strings 1, 2, 3 and 4 with mass per unit length μ, 2μ, 3μ and 4μ respectively. The instrument is played by vibrating the strings by varying the free length in between the range L₀ and 2L₀. It is found that in string -1 (μ) at free length L₀ and tension T₀ the fundamental mode frequency is f₀. List - I List - II (I) String - 1 (μ) (P) 1 (II) String - 2 (2μ) (Q) 1/2 (III) String - 3 (3μ) (R) 1/√2 (IV) String - 4 (4μ) (S) 1/√3 (T) 3/16 (U) 1/16 Answer the following by appropriately matching the lists based on the information given in the paragraph. If the tension in each string is T₀, the correct match for the highest fundamental frequency in f₀ units will be :

I→P,II→Q,III→T,IV→S

I→P,II→R,III→S,IV→Q

I→Q,II→P,III→R,IV→T

I→Q,II→S,III→R,IV→P

Solution:

Correct option is B. I→P,II→R,III→S,IV→Q Fundamental frequency is maximum when length is minimum i.e. L₀,
Case 1. L=L₀, R=T₀, f=f₀; f₁=1/(2L₀√(T₀/μ))
Case 2. f₂=1/(L₀√(2T₀/(2μ)))=f₀/√2
Case 3. f₃=1/(L₀√(2T₀/(3μ)))=f₀/√3
Case 4. f₄=1/(L₀√(2T₀/(4μ)))=f₀/√4=f₀/2