Question

A sound has 13 crests and 15 troughs in 3 seconds. When the second crest is produced the first is 2cm away from the source? Calculate
        a. The wavelength

        b. The frequency

        c. The wave speed

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Answer 1

Answer:

The wavelength will be 4 cm, frequency will be 4.66 Hz and wave speed is 18.6 cm/sec

Explanation:

Given:

No. of crest = 13

No. of trough = 15

Time = 3 seconds

Hence, 1 crest or 1 trough = $\frac{1}{2}\lambda$

therefore,

13 C + 15 T = $28(\frac{1}{2}\lambda)$

=$14\lambda$

Time given 3 seconds

  = $\frac{3}{14}s$

$\nu= \frac{14}{3}$

$\nu= 4.6 Hz \approx 5 Hz$

2 cm distance is travelled is time period

$\lambda = 4 cm$

Again wave will travel in 1 T = 4 cm

wave speed v =$\lambda\times\nu$

= $4\times\frac{14}{3}$

= 18.6 cm/s