Questions of Thought and Discussion - Acoustics | PHYS 170, Study notes of Physics

Download Questions of Thought and Discussion - Acoustics | PHYS 170 and more Study notes Physics in PDF only on Docsity! Chapter 3 Homework Questions for Thought and Discussion 3, 5, 6 Text Exercises 1, 2, 5, 6, 7 1 3.1 What is a Wave? There are (at least) two characteristics common to all waves: • A wave is a traveling disturbance. • A wave carries energy. Most waves require a medium in order for the disturbance to propagate. The exception to this are electromagnetic waves (light waves, radio waves….). These waves can travel in a vacuum. With the exception of electromagnetic waves, it is important to look at the movement of the particles in the medium. Note that the particles have a net displacement of zero over one period. Putting this another way, there is no bulk flow of material – just a movement in the disturbance of the medium. 2 5 The wave number, k, has units of radians/meter and is related to the wavelength Wavelength is similar to the definition of the period. If you remember, the period was the time between two repeated amplitudes on the wave. Wavelength is the distance between two repeated amplitudes on the wave. ! Y =Acos kx±"t+#$ % & ' ( ) ! k= 2" # You are also introduced to equations for finding speeds of waves. The most basic equation is really just the definition of speed put in the lingo of waves… ! v="x "t ! v= " T ! " or ! f = 1 T ! v="f Where, from Chapter 2, T is the period of the wave (in seconds), and is the wavelength of the wave (in meters). The second form of this speed equation was found using the relationship between frequency and period from Chapter 2, . ! " Practice problems: A traveling sound wave has a speed of 350 m/s and a frequency of 440 Hz. What is its wavelength? A traveling wave has a period of 2 seconds and a wavelength of 8 meters. How fast is it moving? 6