Question

A girl sitting on a beach counts six waves passing a buoy in 3.0 s. She measured the distance between the wave crests to be 1.5 meters. What is the speed of the waves the girl observed?​

Answer 1

Given,

Wavelength = 1.5 metres

T = 3 seconds OR 3.0 seconds

We know that the formula of Frequency–

1/Time

According to the question we have seen that Time is 3 seconds

`\sf \longmapsto \: Frequency = (1)/(3 .0 \: seconds)`

`\sf \longmapsto \: Frequency = 0.33 seconds^(-1)`

We Know,

Velocity = Frequency

• Solving Further

`\sf \longmapsto Velocity =0.33 * 1.5`

`\sf \longmapsto \: 0.5 \: m/s ^(-1)`

• Therefore the speed is
  `\sf \: 0.5 \: m/s ^ {-1}`

Answer 2

• wavelength=1.5m
• Time=3s

`\\ \sf\longmapsto Frequency=(1)/(Time)=(1)/(3)=0.33s^(-1)`

Velocity be v

`\\ \sf\longmapsto v=f\lambda`

`\\ \sf\longmapsto V=0.33(1.5)`

`\\ \sf\longmapsto V\approx 0.5ms^(-1)`