Question

A device called oscillator is used to send waves along a stretched string the string is 20cm long, and four complete waves fit along its length when the oscillator vibrates 30 times per second. For the waves on the string:
1. what is their wavelength
2. What is their frequency
3. What is their speed

Answer 1

1.t=d/s=20×30=600

2.600/2=300

3.600/30=20km/nanosecond

Answer 2

Wavelength means distance between consecutive crest or trough so, if we consider wavelength as X then,

20 = 4 x wavelength

So, wavelength = 5 cm

Frequency is the no. of times a body vibrates per second

So according to question

Wave oscillates 30 times per second so,

F = 30 Hz

Wave velocity or speed = f X wavelength

Wave velocity or speed = 30 X 5

So, Wave velocity or speed = 150cm/second