1. Sound Waves Notes http://www.wumag.kiev.ua/20062/P126_1.jpg

2. Section 1 Waves

3. Characteristics of Waves
Waves are everywhere.
Examples include: sound waves, visible light waves, radio waves, microwaves, water waves, sine waves, cosine waves, stadium waves, earthquake waves, waves on a string, and slinky waves.

4. What are Waves?
A wave is a disturbance that travels through a medium without the transfer of material, from one location to another location.
The repeating and periodic disturbance which moves through a medium from one location to another is also referred to as a wave.

5. The Wave Equation
The only equation you need for waves is Velocity or Speed = Frequency x Wavelength v = f x l This equation is important! The equation can be rearranged to give f = v ÷ l or l = v ÷ f Note - always make sure that you give the units for your answer and that the units are correct. If the wavelength is given in centimeters, convert it to meters before doing the calculation.

6. Practice Calculations.
Q1. A sound wave has a frequency of 3250 Hz and a wavelength of 0·1 m. What is its velocity? Use v = f x l
V = 3250 x 0·1
V = 325 m/s.

7. Practice Calculations.
Q2. A sound wave travels with a velocity of 330 m/s and has a frequency of 500 Hz. What is its wavelength? Use l = v ÷ f
l = 330 ÷ 500
L = 0·66 m.

8. Practice Calculations.
Q3. A wave at sea travels with a velocity of 25 m/s. If it has a wavelength of 10 m, what is its frequency? Use f = v ÷ l
f = 25 ÷ 10
f = 2·5 Hz.

9. When the slinky is stretched from end to end and is held at rest, it assumes a natural position known as the equilibrium or rest position. The coils of the slinky are spaced equally far apart.

10. The act of moving the first coil of the slinky in a given direction and then returning it to its equilibrium position creates a disturbance in the slinky.
Think of the medium as a collection of interacting particles. In other words, the medium is composed of parts which are capable of interacting with each other.
A pulse is a single disturbance moving through a medium from one location to another location.
sound waves

11. Types of Waves
Wave types are based on the direction of movement of the individual particles of the medium relative to the direction which the waves travel.
Three types: transverse waves, longitudinal waves, and surface waves.

12. A transverse wave is a wave in which particles of the medium move in a direction perpendicular to the direction which the wave moves.
Types of Waves

13. A longitudinal wave moves through a material, the particles of the material move backwards and forwards along the direction in which the wave is traveling.
Rarefaction is the name given to the region where the coils of the spring are pulled apart.
Compression is the name given to the region where the coils of the spring are pushed together.
Waves which travel within the depths of the ocean are longitudinal waves.

14. A surface wave is a wave in which particles of the medium undergo a circular motion. Surface waves are neither longitudinal nor transverse. The waves which travel along the surface of the oceans are referred to as surface waves.

15. Waves in a Medium
Waves traveling through a solid medium can be either transverse waves or longitudinal waves.
Waves traveling through the bulk of a fluid are always longitudinal waves.
Transverse waves require a relatively rigid medium in order to transmit their energy.
Any wave moving through a medium has a source.

16. Comparing Longitudinal and Transverse Waves

17. Properties of Waves
Amplitude: the height of the wave, measured in meters.
Wavelength: the distance between adjacent crests, measured in meters or the distance the wave has traveled during one complete cycle
Period: the time it takes for one complete wave to pass a given point, measured in seconds.
Frequency: the number of complete waves that pass a point in one second, measured in inverse seconds, or Hertz (Hz). 1 Hz is equivalent to 1 cycle/second.
Speed: the horizontal speed of a point on a wave as it propagates, measured in meters / second.

18. Speed = wavelength / period OR wavelength x frequency

19. Frequency and Period of a Wave
Since the symbol f is used for frequency and the symbol T is used for period, these equations are also expressed as:

20. The crest of a wave is the point on the medium which exhibits the maximum amount of positive or upwards displacement from the rest position. The trough of a wave is the point on the medium which exhibits the maximum amount of negative or downwards displacement from the rest position.

21. Traveling Waves
Traveling waves are observed when a wave is not confined to a given space along the medium. The most commonly observed traveling wave is an ocean wave.
This wave pattern continues to move in uninterrupted fashion until it encounters another wave along the medium or until it encounters a boundary with another medium.

22. Standing Waves
Because the observed wave pattern is characterized by points which appear to be standing still, the pattern is often called a standing wave pattern.

23. Standing Waves
Point A on the medium moves from a maximum positive to a maximum negative displacement over time. These points are called antinodes - the opposite of nodes. Point B on the medium is a point which never moves. Point B is a point of no displacement. Such points are known as nodes

24. Interactions of Waves reflection, refraction, diffraction,
and interference

25. Reflection. Any type of wave can be reflected.
Reflection best occurs from flat, hard surfaces.
After reflection, a wave has the same speed, frequency and wavelength,
It is only the direction of the wave that has changed.

26. The light ray which hits the mirror is called the incident ray.
The light ray which bounces off the mirror is called the reflected ray.
The angle of incidence equals the angle of reflection, i = r.
This means that whatever angle the light ray hits the mirror, it will be reflected off at the same angle.

27. Behavior of water waves are reflected from hard flat surfaces.
Water Waves - Reflection.
Behavior of water waves are reflected from hard flat surfaces.
> The wave peak stays the same where it is being reflected.
The red part of the incident wave plus the blue part of the
reflected wave is the same as the original line.
After reflection, a wave has the same speed, frequency and
wavelength, it is only the direction that has changed.

28. Refraction
Refraction - is when a wave moves from one medium into another medium at an angle, it changes speed as it enter the second medium, which causes it to bend Bending only occurs when a one side of the wave enters the new medium before the other side of the wave.

29. Water Wave Refraction
Water waves travel faster on the surface of deep water than they do on shallow water. The change in speed of the wave will cause refraction. The change in speed has changed the direction of the wave.

30. Water Wave Refraction
The slower wave in the shallow water has a smaller wavelength.
The amount of refraction increases as the change in speed increases.

31. Diffraction Any type of wave can be diffracted.
A diffracted wave will "spread out".
Diffraction occurs when the wavelength of a wave is of a similar size to an obstacle or a gap in a barrier.
After diffraction, a wave will have the same speed, frequency and wavelength.