MCQ
Two waves of wavelengths $99\, cm$ and $100\, cm$ both travelling with velocity $396\, m/s$ are made to interfere. The number of beats produced by them per second is
- A$1$
- B$2$
- ✓$4$
- D$8$
✓
Answer
Correct option: C.
$4$
c
Velocity of wave $\mathrm{v}=\mathrm{n} \lambda$
Velocity of wave $\mathrm{v}=\mathrm{n} \lambda$
where $\mathrm{n}=$ frequency of wave $\Rightarrow \mathrm{n}=\frac{\mathrm{v}}{\lambda}$
$\mathrm{n}_{2}=\frac{\mathrm{v}_{2}}{\lambda_{2}}=\frac{396}{100 \times 10^{-2}}=396 \mathrm{Hz}$
no. of beats $=n_{1}-n_{2}=4$
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