2. Waves Nature and Properties of Wave Definition of wave : Disturbances moving from some sources to the surrounding area Next Slide Transverse wave and Longitudinal wave Examine pulses along a spring (transverse wave) Diagram Photo Introduction 1

3. Waves Basic Terms of Wave Next Slide Example (Transverse wave) A pulse travelling on a string Diagram Basic terms to describe a wave : amplitude (A), wavelength ( ), frequency (f), period (T), wave speed (v) Diagram Introduction 2

4. Waves Motions in a wave Next Slide Motion of particles in a transverse wave Diagram Graphs we use to describe a transverse wave as well as the motion of particles inside the wave Diagram Reflection and superposition of pulses in a string Diagram Introduction 3

5. Waves Stationary wave Basic arrangement for producing stationary wave : When a long spring is stretched on a smooth floor, with one end fixed and the other end repeatedly flicked sideways, a train of wave is produced. The addition of the incident wave and the reflected wave forms a special wave called a stationary wave. Next Slide Diagram Stationary Wave 1

6. Waves Properties of a standing wave Pattern of a standing wave Next Slide Diagram Important differences between a standing wave and a transverse wave Diagram Stationary Wave 2

7. END of Waves

8. Waves Next Slide Ripples created in a water tank Paper vibrated by sound Introduction 1

9. Waves Click Back to Particles vibrated by a spring Back to Introduction 1

10. Waves Next Slide Transverse wave transverse wave in a spring transverse wave in a string with small beads Introduction 1

11. Waves Next Slide Definition of a transverse wave : a wave with the disturbances vibrating at right angles to the direction of travel (direction of energy transmit) of the wave direction of travelling of the wave vibration of particles Introduction 1

12. Waves Next Slide Longitudinal wave longitudinal wave in sound longitudinal wave in a string with small beads Introduction 1

13. Waves Click Back to Definition of a longitudinal wave : a wave with the disturbances vibrating along the direction of travel (direction of energy transmit) of the wave direction of travelling of the wave vibration of particles Back to Introduction 1

14. Waves Click Back to A transverse wave is shown below : Back to Introduction 2

15. Waves Click Back to A pulse travelling on a spring : Back to Introduction 2

16. Waves Next Slide A transverse wave is shown below : crest trough Introduction 2

17. Waves Next Slide Amplitude (A) : the size of the maximum disturbance measured from the resting position (unit : m) Wavelength ( ) : the minimum distance in which a wave repeats itself (unit : m) Frequency (f) : the number of complete waves produced in one second (unit : Hz) Period (T) : the time taken for a particle to make one complete vibration (unit : s) Wave speed (v) : the speed of propagation of wave (unit : m/s) Introduction 2

18. Waves Click Back to Back to A direction of travel v (speed) one complete vibration (different forms) T : time required for one complete vibration f : no. of complete vibrations in one second Introduction 2

19. Waves Next Slide t = 0 s = 0 T t = 1 s = 1/4 T t = 2 s = 1/2 T t = 3 s = 3/4 T t = 4 s = 1 T A B C D E Introduction 3

20. Waves Next Slide A transverse wave with : A = 1 m, = 2 m, T = 4 sec, f = 1/T = 1/4 Hz (times per sec), v = f = 0.5 m/s Particles A, D and E are exactly one wavelength apart, they vibrate in phase. These particles have exactly the same motion at any time. Particles A and C are exactly half a wavelength apart, they vibrate out of phase. These particles have exactly the opposite motion at any time. Introduction 3

21. Waves Click Back to Particle C seems to be trying to catch up with B, but never succeeds. These particles vibrate neither in phase nor out of phase. We say that B leads C or C lags behind B. Motion of particle A : i. When t = 1 s (1/4 T), particle A is momentarily at rest. ii. When t = 2 s (1/2 T), particle A is moving up. iii. When t = 3 s (3/4 T), particle A is momentarily at rest. iv. When t = 4 s (1 T), particle A is moving down. Back to Introduction 3

22. Waves Next Slide A transverse wave is shown below : direction of travel A B Introduction 3

23. Waves Next Slide Displacement of particles vs distance graph of the wave at a certain time : 0 distance displacement The graph shows the displacements of the particles at different positions in the wave. The shape of the graph is the same as that of the wave itself. Introduction 3

24. Waves Click Back to Displacement vs time graphs of particle A and particle B in the wave : The graph shows the motion of a particle in the wave. It’s shape varies for different particles. 0 time displacement A B Back to Introduction 3

25. Waves Next Slide A pulse travelling on a string with a fixed end. A pulse travelling on a string with a free end. incident pulse reflected pulse incident pulse reflected pulse Introduction 3

26. Waves Next Slide The pulse travels with a constant speed along the spring and its amplitude decreases gradually. The pulse speed increases when the spring is stretched more. The pulse is reflected at the fixed end, and the reflected pulse is always opposite to the incident pulse. Introduction 3

27. Waves Click Back to The superposition of the two pulses is shown below : Back to Introduction 3

28. Waves Next Slide The superposition of the incident wave and reflected wave on a long spring is shown : incident wavereflected wave long spring Stationary Wave 1

29. Waves Click Back to At last, the pattern of the string will become : Back to ANANANANANANANAN A : Anti-node ( points with maximum amplitude) N : Node (points with zero amplitude) distance between successive nodes or anti-nodes is equal to /2 Stationary Wave 1

30. Waves Click Back to t = 0 T t = 1/8 T t = 1/4 T t = 3/8 T t = 1/2 T t = 5/8 T t = 3/4 T t = 7/8 T Back to Stationary Wave 2

31. Waves Click Back to Back to Stationary WaveTravelling Wave does not move to any direction moves to a direction (v  0) amplitude is not the same for all particles amplitude is the same for all particles energy is stored inside the wave at certain positions energy is transmitted to other places through the wave Stationary Wave 2