Question

Consider a sinusoidal travelling wave shown in figure. The wave velocity is $+40cm/s$. Find the frequency.

• A. $2Hz$
  
• B. $6Hz$
  
• C. $8Hz$
  
• D. $10Hz$
  

Answer 1

The correct option is D $10Hz$

Clearly from figure, the wavelength is equal to the distance between two in-phase points.
Let us consider the points where it cuts the x-axis.

The in-phase points cut x-axis at $2.5cm$ and $6.5cm$.

Thus the wavelength is $4cm$
We have $v=\lambda \nu$

$⟹\nu =\frac{v}{\lambda }=\frac{40cm/s}{4cm}=10Hz$