Week 2- Getting familiar with waves

Q1 In a recording room an acoustic wave was measured to have a frequency of 1KHz. What would its wavelength in cm be?

λ=v/f
λ= 340/1000
λ= 0.34m
λ=34cm



Q2 If a violinist is tuning to concert pitch in the usual manner to a tuning fork what is the likely wavelength of the sound from the violinist if she is playing an A note along with sound from the pitch fork?

freq. of note at orchestral  A = 440 Hz

T=1/f
T=1/440
T=0.0027

Q3 If an acoustic wave is travelling along a work bench has a wavelength of 3.33m what will its frequency be? Why do you suppose that is it easier for this type if wave to be travel through solid materials?

f=v/λ
f=4000/3.33
f=1201.2 Hz

the molecules in a solid are more tightly compact

Q4 Sketch a sine wave accurately of amplitude 10, frequency 20Hz. Your sketch should show two complete cycles of wave. What is the duration  of one cycle? What is the relationship between the frequency and the duration of one cycle?

Q5 Research the topic “Standing Waves”. Write a detailed note explaining the term and give an example of this that occurs in real life. (Where possible draw diagrams and describe what represent)



A Standing Wave is a wave form that does not seem to travel. They are caused by two waves moving in opposite directions with the same amplitude and frequency, causing interference. The string has two points, a maximum and minimum, the maximum is called an anti-node and the minimum, a node.

When the two waves collide they combine to form a Standing Wave.

An example of a standing wave would be in a Guitar or Violin. The two points of the string are fixed (the nut and bridge) and therefore the waves cannot ‘travel’ and hence a standing wave occurs.

Q6 What is meant by terms constructive and destructive interference?

interference is when two waves meet, constructive interference is when the two waves are 'in phase' (the peaks and troughs are the same). When the interference is constructive, the amplitude increases, making the signal stronger. For Destructive interference is the exact opposite, the waves are not in phase and the amplitude decreases, making the signal weaker.
Q7 What aspect of an acoustic wave determines its loudness?

The amplitude

Q8 Why are decibels used in the measurement of relative loudness of acoustics waves?

Decibels are used because it is a logarithmic measurement that reflects the range of sound intensity our ears can hear and how we perceive loudness

Q9 How long does it take a short 1KHz pulse of sound to travel 20m verses a 10Hz pulse?

It would take the same amount time.

Q10 Does sound travel under water? If so what effect does the water have?

Yes, it speeds the sound up to 1500 m/s