1. Categories of wave
2. The anatomy of the wave
3. Electromagnetic wave
4. Machnical wave
5. Electromagnetic waves
6. Light
7. Standing wave
8. Frequency
9. wavelength
10. Wave porperties
11. Spectrum
12. benefit of electrimagnetic wave
13. Magnetic field
14. Electric field
15. The absorotion of light
16. Visible light
17. The effect of light on life
18. Soruce of sound
19. Benefit of light
20. Sound intensity
21. Beat
22. Resonance
23. Noise pollution
24. Sound Quality
25. High - Low pitched
26. High- low tone
27. reflection
    1. mirror
28. refraction
29. Interference
30. Diffraction
31. Benefit of light
    1. optical instrument
    2. mirror
    3. Glasses
    4. Fiber optic
32. Photograph
33. Sound