Types of Wave and the Wave Motion

Question Figure 13.1 shows an arrow that indicates the direction of travel of a wave in a medium. A is a particle of the medium that is in the path of the wave. (a) Draw diagrams to show how the particle moves when the wave is: (i) A transverse wave (ii) A longitudinal wave [2marks] b. A transverse wave has a wavelength of 50millimetres, a frequency of 40Hertz and an amplitude of 20millimetres: (i) State what is meant by frequency of wave (ii) Draw a full-scale diagram of the wave at one instant, showing two complete wavelengths; (iii) Calculate the speed of the wave. (iv) Give two examples of a transverse wave [7marks] c. Describe an experiment that you could perform to measure the speed of sound in air. In your account, you should: (i) Draw a labelled diagram of the apparatus you would use; (ii) Describe how the experiment is performed; (iii) State the readings that are taken; (iv) Show how the readings are used to calculate the speed of sound [6 marks] Solution (i) In a transverse wave it moves in up and down manner like in this figure: (i)In a longitudinal wave it moves in back and forth manner like in this figure: Remember that, in a transverse wave, the oscillations are perpendicular to the wave direction whereas in a longitudinal wave, the oscillations are along the wave direction. In terms of frequency of wave (Number of oscillation per second), each point along the wave undergoes 40 complete oscillations in one second. (b) (i) Wavelength is the distance between two successive crests or troughs or any two points that are in phase. (ii) Wavelenght =50millimetres =50times10 to the power of minus 3m; frequency=40Hertz we now calculate the speed of the wave: wave speed=frequency times wavelenght=(40)times (50times10to the power of minus 3 m)=2.0metres per second (iii) Examples of a transverse wave include: Water wave, light wave, etc. (c) (i) The speed of sound in air can be measured using a drum and stowatch, and facing a sound barrier such as a tall wall like in this figure: (ii) The experiment will proceed as follows: The observer hits the drum and starts the stopwatch. When the observer hears the echo, the stopwatch is stopped. (iii) To take the readings, The distance from the observer to the wall (d) is measured. The time reading on the stopwatch (t) is noted. (iv) The readings are used to calculate the speed of sound through this ratio: Speed of sound=distance over ime=2 times distance over time (We double the distance because we consider the distance covered while going and the distance covered while coming back)