1. Resource _ http://coolsciencelab.com/sixth_grade.htm
WAVES
Unit C
Resource _

2. Big Ideas
1.1 Waves Transfer energy
1.2 Waves have measurable properties
1.3 Waves behave in predictable ways.

3. The Nature of Waves
What is a wave?
A wave is a repeating disturbance or movement that transfers energy through matter or space

4. Waves transfer energy not matter.
The water waves below are carrying energy but are not moving. Waves can only exist as they have energy to carry.

5. *Mechanical waves are waves which require a medium.
A medium is a form of matter through which the wave travels (such as water, air, glass, etc.)
*Waves such as light, x-rays, and other forms of radiation do not require a medium.

6. What are the two kinds of mechanical waves?
Transverse
Longitudinal

7. Transverse Waves
In a transverse wave the matter in the wave moves up and down at a right angle to the direction of the wave
Transverse waves— The motion of particles is at 900 angles
Example – rope, water waves, light waves

8. Example of a transverse wave:

9. Water waves transfer energy through matter (mechanical waves):
Particles of water move around in circles. The farther below the surface,
the smaller the circle.

10. Also called compression waves
Longitudinal Waves
In a longitudinal wave the matter in the wave moves back and forth, parallel to the direction of the wave.
Observe the red line
Also called compression waves

11. You can see the result of vibrations that create motion in the water to produce waves on the beach.
As the wave slows, its crest and trough come closer together. The top of the wave is not slowed by friction and moves faster than the bottom.

12. Longitudinal vs. Transverse Waves
Sound
05/02/2006
Longitudinal vs. Transverse Waves
Sound is a longitudinal wave, meaning that the motion of particles is along the same direction of the force
Lecture 10

13. What are earthquake waves (seismic waves)?
An energy wave that
--vibrates through the earth’s crust as the crust bends or breaks.
--seismic waves produce both transverse and longitudinal waves.
--Some travel through the earth and some travel across the earth’s surface.

14. Anatomy of a Seismic Wave
When the Earth’s crust breaks, energy that is
released transmits outward, causing an
earthquake. Some waves travel through the earth
and some travel across the earth’s surface.

15. longitudinal, sound waves and seismic waves have in common?
What do transverse,
longitudinal, sound waves and seismic waves have in common?
They all must travel through a MEDIUM…..any matter (air, water, ground)
Electromagnetic waves DO NOT require a medium.

16. Examples of electromagnetic waves
Radio waves
Microwaves
infrared waves
ultraviolet light (UV light from sun)
X-rays
gamma-rays

17. What are the parts of a transverse wave?
The crest is the highest point on a transverse wave.
The trough is the lowest point on a transverse wave.
The rest position or fixed position of the wave is called the node or nodal line.

18. What is a wavelength?
The wavelength is the distance from one crest to another crest or the distance from one trough to another trough.

19. Parts of a wave
Wave height
Wavelength
Crest
Crest
Trough

20. Longitudinal (Compressional) wave
On a longitudinal wave the area squeezed together is called the compression.
The areas spread out are called the rarefaction.

21. Longitudinal (compressional) wave
The wavelength is the distance from the center of one compression to the center of the next compression.

22. Important Wave Terms
Wavelength (λ) is a measure of distance, so the units for wavelength are always distance units, such as meters, etc
Frequency (f) is the number of waves that pass through a point in one second. The unit for frequency is waves per second or Hertz (Hz). One Hz = One wave per second
The amplitude of a wave is directly related to the energy of a wave

23. How are Frequency and Wavelength Related?
The smaller the wavelength, the more times it will pass through a point in one second. The larger the wavelength, the fewer times it will pass through a point in one second.
Period is the time it takes for one full wavelength to pass a certain point.

24. The amplitude in a longitudinal wave depends on how dense the medium is
at each compression
High amplitude
Low amplitude A B .

25. What is amplitude?
The amplitude of a transverse wave is determined by the height of the crest or depth of the trough.

26. The Behavior of Waves
What is reflection?
When a wave bounces off an object and changes direction – this is reflection.

27. What is refraction?
Refraction is the bending of a wave as it passes from one medium to another.
A wave travels at different speeds in different things. When a wave traveling a certain speed moves into another medium, it will either increase in speed or decrease in speed, resulting in a change in direction.
The pencil looks like it is broken at the
surface of the water because of Refraction

28. If you are in a swimming pool under water and
look up and saw a ball, Is the ball really directly above you?

29. Refraction

30. What is diffraction?
Diffraction occurs when an object (island) causes a wave to change direction and bend around it.

31. Diffraction also occurs when passing through a small opening
Diffraction also occurs when passing through a small opening. They diffract and spread out as they pass through the hole.

32. What is wave interference?
Waves interfere in one of two ways: Constructive Interference and Destructive Interference.

34. Warm up Name, Date - 2/20/1011
How many centimeters (cm) are on the graph? Each green mark on the
horizontal line represents a cm.
2. How many cm did the wave travel?
3. How many wavelengths are on the graph?

35. The End

36. Examples of electromagnetic waves
Radio waves
Microwaves
infrared waves
ultraviolet light (UV light from sun)
X-rays
gamma-rays