Wave equation (speed, wavelength & frequency

This ppt discusses the relationship of wavelength and frequency to the speed of the wave.

1. Do now! Can you write the title “ WAVE EQUATION ” in your NOTE BOOK please? (DO NOT FORGET THE LECTURE NUMBER)

2. WAVE EQUATION

3. What is a wave? YouTube - Water bubble in Space (zero gravity) http://www.youtube.com/watch?v=xUnadiyPTks

4. Waves Waves can transfer energy and information without a net motion of the medium through which they travel . They involve vibrations (oscillations) of some sort. Can you do something very boring and traditional……… Can you copy this please?

5. Rays highlight the direction of energy transfer . Light RAY UV RAY GAMMA RAY

6. Transverse waves The oscillations are perpendicular to the direction of energy transfer. Direction of energy transfer Oscillations CREST T rough

7. Transverse waves Water ripples Light On a rope/slinky Earthquake

8. Longitudinal waves The oscillations are parallel to the direction of energy transfer . Direction of energy transfer oscillation

9. Longitudinal waves compression rarefaction

10. Longitudinal waves Sound Slinky Earthquake

11. Wave measurements

12. Amplitude - A The maximum displacement from the mean position . A mplitude THE MAXIMUM DISPLACEMENT FROM THE NORMAL LINE OR EQUILIBRIUM Equilibrium/normal line

13. The time taken (in seconds) for one complete oscillation. It is also the time taken for a complete wave to pass a given point is called PERIOD. One complete wave

14. Frequency - f The number of oscillations in one second. Measured in Hertz. 50 Hz = 50 vibrations/waves/oscillations in one second .

15. Period and frequency Period and frequency are reciprocals of each other f = 1/T T = 1/f

16. Wavelength - λ The length of one complete wave. wavelength THE LENGTH OF ONE COMPLETE WAVE

17. Wave speed - v The speed at which the wave fronts pass a stationary observer. YouTube - Bill Nye the Science Guy - 51: Waves 1/3 THE SPEED AT WHICH THE WAVE FRONTS PASS A STATIONARY OBSERVER

18. The Wave Equation v = f λ v = speed (m/s) λ = wavelength (m) f = frequency (Hz ) v λ f x

19. A water wave has a frequency of 2Hz and a wavelength of 0.3m. How fast is it moving? A water wave travels through a pond with a speed of 1m/s and a frequency of 5Hz. What is the wavelength of the waves? Some example wave equation questions 0.2m 0.6m/s

20. 3.)The speed of sound is 330m/s (in air). When Dave hears this sound his ear vibrates 660 times a second. What was the wavelength of the sound? 4.)Purple light has a wavelength of around 6x10 -7 m and a frequency of 5x10 14 Hz. What is the speed of purple light? 0.5m 3x10 8 m/s

21. SAMPLE PROBLEM 1. A wave has frequency of 50 Hz and a wavelength of 10 m. What is the speed of the wave ? 2. A wave has frequency of 5 Hz and a speed of 25 m/s. What is the wavelength of the wave? 500m/s 5m

22. 3 ) A wave has wavelength of 10 m and a speed of 340 m/s. What is the frequency of the wave? 4. The speed of a wave is 65 m/sec. If the wavelength of the wave is 0.8 meters, what is the frequency of the wave? 5. A wave with a frequency of 500 Hz is traveling at a speed of 200 m/s. What is the wavelength? 34 Hertz/ 34 vib /sec 85 Hertz/ 85 vib /sec 0.4m

23. Wave equation questions v λ f x

24. 1. As the wavelength of a wave in a uniform medium increases, its speed will _____. a . decrease b. increase c. remain the same

25. EXPLANATION ALL EM WAVES TRAVEL AT THE SPEED OF LIGHT REGARDLESS OF THE FREQUENCY AND WAVELENGHT. The speed of light is close to 300,000 km/s (186,300 miles per second). Another way of writing this is : 3x 10 8 m/s -1

26. 2. As the wavelength of a wave in a uniform medium increases, its frequency will _____. a . decrease b . increase c . remain the same

27. Let’s try some questions! ACTIVITY TIME!

28. ACTIVITY NO____ SPEED (m/s) Wavelength (m) Frequency (Hz) 1._______ 9m 4Hz 36m/s 2.________ 6Hz 330m/s 27m 3. ________ 750m/s 4. _______ 10Hz 5.________ 250m 15 Hz 6.________ 2m 3Hz

29. LET’S CHECK!

30. ACTIVITY NO____ SPEED (m/s) Wavelength (m) Frequency (Hz) 1._______ 9m 4Hz 36m/s 2.________ 6Hz 330m/s 27m 3. ________ 750m/s 4. _______ 10Hz 5.________ 250m 15 Hz 6.________ 2m 3Hz 36m/s 6m 12.2 Hz 75m 3750m/s 6m/s