Question

$P$ and $Q$ are two wires whose fundamental frequencies are $256Hz$ and $382Hz$ respectively. How many beats in two second will be heard by the third harmonic of $A$ and second harmonic of $B$?

• A. $4$
• B. $8$
• C. $16$
• D. $zero$

Answer 1

The correct option is B $8$

Third harmonic of $A,n=256\times 3=768Hz$

Second harmonic of $B,n^{\prime }=382\times 2=764Hz$

Number of beats per second $=n-n^{\prime }$

$=768-764=4Hz$

Number of beats in two second $=4\times 2=8Hz$