1. Waves And Wave Properties Applied Physics and Chemistry SHM Lecture 2

2. Wave A disturbance that transmits energy Mechanical waves: require a medium to move  Transverse waves  Longitudinal waves

3. Transverse Wave Movement perpendicular to direction of wave Example: light

4. Longitudinal Wave Movement parallel to direction of wave Series of compressions and rarefactions Example: sound

5. Measuring the Wave Speed: depends on the medium  Measured in m/s Amplitude: maximum displacement from rest Wavelength: distance between points where wave pattern repeats Frequency: number of waves that pass a point in one second  Measured in Hertz (Hz): 1 Hz is one wave/second

7. Wave Equation Relates frequency, velocity and wavelength V = f λ There is also a relationship between period and frequency T = 1/f

8. Sample Problem A sound wave has a frequency of 192 Hz and travels the length of a football field (91.4 m) in 0.271 s. What is the speed of the wave? Known: f=192 Hz d=91.4 m t=0.271 s Equation: V=d/t (no known λ)‏ Solve: V=(91.4m)/(0.271 s) = 337 m/s

9. Sample Problem Continued Find the wavelength of the wave. Known: V=337 m/s f=192 Hz Equation V=fλ so λ=V/f Solve: λ=(337 m/s)/192 Hz So λ= 1.76 m

10. Sample Problem Continued What is the period of the wave? Known: f=192 Hz Equation: T=1/f Solve: T=1/192 Hz T=0.00521 s

11. Sample Problem Continued If the frequency was changed to 442 Hz, what would the new wavelength be? Known: V=337 m/s f=442 Hz Equation: V=fλ so λ=V/f Solve: λ=(337 m/s)/(442 Hz)‏ And λ=0.762 m

12. Now you try it! Solve the problems on your worksheet! Remember the wave equation and the relationship between period and frequency.