# 07 waves

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### 07 waves

1. 1. The Wave
2. 2. WAVES Nature, Properties and Characteristics
3. 3. Wave, Pulse Wave and Periodic Wave • WAVE – a disturbance or variation traveling through a medium or a vacuum • Pulse wave – a single traveling unrepeated disturbance • Periodic Wave – succession of periodic disturbances
4. 4. IMPORTANT Waves are simply energy carriers. As the wave travels through a medium, the energy it carries is transmitted as vibrational energy from one particle to another. The particles of the medium do not move or go with wave.
5. 5. WAVE Types: 1. MECHANICAL WAVES – waves that requires a medium for propagation Examples: sound waves, water waves 2. ELECTROMAGNETIC WAVES (EM) – waves that can travel through a medium or through vacuum Examples: light, radio waves, gamma rays
6. 6. Group Activity: Human Simulation Discuss the following questions: • What is a transverse/longitudinal wave? • What is frequency? wavelength? amplitude? Then, simulate your assigned wave using your own bodies to show the following: • wave with low frequency and low amplitude • wave with high frequency and low amplitude • wave with low frequency and high amplitude • wave with high frequency and high amplitude
7. 7. Then, simulate your assigned wave using your own bodies to show the following: Group Activity: Human Transverse: • wave with low frequency and low amplitude • wave with high frequency and low amplitude • wave with low frequency and high amplitude • wave with high frequency and high amplitude Simulation Longitudinal: • Wave with low frequency • Wave with high frequency • Wave with short wavelength • Wave with long wavelength
8. 8. Types of Mechanical Waves: a. Transverse Waves – the particles of the medium vibrates perpendicular to the direction of the wave motion b. Longitudinal Waves – the particles of the medium vibrates parallel to the direction of the wave motion c. Surface Waves – combination of transverse and longitudinal motion
9. 9. WAVE Parameters crest amplitude equilibrium position wavelength trough (1 λ) 1. crest – the highest point/position in a transverse wave 2. trough – the lowest point/position in a transverse wave
10. 10. WAVE Parameters crest amplitude equilibrium position wavelength trough (1 λ) 3. equilibrium position – initial position of the particles of the medium before the waves passed through 4. amplitude – perpendicular distance from the equilibrium position to either the crest or the trough
11. 11. WAVE Parameters crest amplitude equilibrium position wavelength trough (1 λ) 5. wavelength ( λ ) – distance between two successive and similar positions in a wave (could be between two successive crests or troughs)
12. 12. WAVE Parameters crest amplitude equilibrium position wavelength trough (1 λ) 6. frequency ( f ) – number of waves that passes a certain point per second 7. period ( T ) – time (in seconds) it takes a wave to travel a distance equal to a wavelength
13. 13. WAVE Parameters crest amplitude equilibrium position wavelength trough (1 λ) 8. wave speed or velocity ( v ) – linear distance traveled by the wave per unit time
14. 14. WAVE Parameters a. Compression - region of wave with highest pressure or density; happens when molecules are forced, or pressed, together. b. Rarefaction - region of wave with lowest pressure or density; occurs when molecules are allowed to expand
15. 15. fin
16. 16. General Properties REFLECTION The turning back or bouncing back of waves after hitting an obstacle.
17. 17. General Properties REFRACTION The change in direction and change in wavelength or velocity of waves (bending) as it passes through different medium or through the same medium of varying temperatures.
18. 18. General Properties DIFFRACTION The spreading or bending of waves through an opening or around an obstacle.
19. 19. General Properties INTERFERENCE The meeting or coming together of waves. Interference could be CONSTRUCTIVE – waves reinforce each other or DESTRUCTIVE – waves cancel each other. Interference may also be described as partial or total.
20. 20. WAVE Speed (v) v = distance traveled by a wave / time taken v= d/t v = wavelength / period = λ / T v = wavelength x frequency = λf NOTE: EM waves travel through vacuum at 299, 792, 458 m/s or around 300 000 000 m/s (3 x 108 m/s). This speed is considered to be the speed of light in a vacuum denoted by the letter c (c =3x108m/s.)
21. 21. Sample Calculations 1. AM radio signals/waves (EM waves) have average wavelength of around 370m. What is the frequency of this signal in Hz? In kHz? 2. A swimmer notices that water wave crests pass his body every 5s. His estimate of the distance between two crests is 3m. How fast are the waves traveling? 3. Light waves (EM waves) coming from the sun have frequencies of 6 x 1014 Hz. If it will take this wave 8 minutes to travel from the sun to the Earth, how far is the sun from us? 4. A certain radio wave has a wavelength of 300m. What is the frequency of this wave in Hz? In kHz?