Q 11-14-022NEETJEE MainMedium
Two sound waves of wavelengths $1.00$ m and $1.01$ m produce $4$ beats per second. The speed of sound is
Answer: (B) $404$ m/s
Concept. Beat frequency $= f_1 - f_2 = v\left(\dfrac{1}{\lambda_1} - \dfrac{1}{\lambda_2}\right)$.
Step 1. Set up.
$$v\left(\frac{1}{1.00} - \frac{1}{1.01}\right) = 4 \;\Rightarrow\; v \times \frac{0.01}{1.01} = 4$$
Step 2. Solve. $v = 404$ m/s.
Answer. $404$ m/s (Option B).
Solution by Sreeraj P, M.Sc Physics