Question

The distance between the first and third crests in a sinusoidal wave is 20 cm. If the source produces 10 waves in 1 s, then the velocity of the wave is

• A. $40m/s$
• B. $20m/s$
• C. $10m/s$
• D. $2m/s$

Answer 1

The correct option is C $10m/s$

The peak value of amplitude is called crest. The distance between two continuous crests is called wavelength $\left(\lambda \right).$

Distance between first and third crest, $AB=2\lambda$

Now, $2\lambda =20cm\Rightarrow \lambda =10cm=0.1m$

According to the question, the source produces 10 waves in 1 s.

$\therefore$ Frequency of the wave, $f=10Hz$

Let the velocity of the wave be v.

$v=\lambda f\Rightarrow v=0.1\times 10\Rightarrow v=1m/s$

Hence, the correct answer is option (c).