1. Waves
Chapter 15

2. Waves Wave a disturbance that carries energy through matter or space
If there is a leaf floating on water and a wave comes through the area the leaf will not move with the wave
After the wave passes the leaf will return to its original location
The only thing to pass with the wave is energy

3. Waves Most waves travel through a medium
Medium matter through which a wave travels
Air
Water
Mechanical waves require a medium
Most waves are mechanical waves

4. Waves Electromagnetic waves waves that do not require a medium
light does not need a medium
The light that the sun radiates can travel to earth through empty space meaning no medium
Radio waves are another example of electromagnetic waves

5. Waves Energy is the ability to do work
We know waves have energy because they can do work
Sound waves do work on our ear drum
Water waves do work on boats
The larger the wave the more energy it has
Tsunamis’ are huge waves that have enough energy to destroy coastal land and homes (which is essentially doing work to this area)

6. Waves The energy waves have spread out as it travels through a medium
If you stand right next to a loud speaker this could damage your ear drum
If you stand 100 meters from the speaker it will not damage your ear drum
The reason for this is because waves spread out and lose energy as they spread out in space

7. Waves & Vibrations Most waves are caused by vibrations
Sound waves are produced by the vibration of vocal cords
Electromagnetic waves are cause by charged particles vibrating

8. How we hear Sound waves travel through the area
Sound waves are gathered by the tympanic membrane of the ear
The tympanic membrane vibrates the bones in the ear to amplify the sound
The vibrations made by the bones trigger electrical pulses to our brain which decipher sounds

10. Harmonic Motion
If you have a spring and pull it down and release it the spring will bounce up and down until it releases all of its energy simple harmonic motion
If you have masses connect by springs and you cause one mass to vibrate the vibrations will move to each mass through the springs that connect them this is called damped harmonic motion

11. Transverse waves
Transverse wave is a wave in which the wave motion is perpendicular to the particle motion
Examples electromagnetic waves

12. Longitudinal waves
Longitudinal wave is a wave in which the wave motion is parallel to the particle motion
Examples sound waves

13. Parts of a transverse wave

14. Parts of a longitudinal wave

15. Surface waves Surface waves are water waves
The particles move both perpendicularly and parallel to the direction in which the wave travels
Surface waves move in an ellipse

16. Surface wave

17. Wave properties
Amplitude from the rest point to the trough or the rest point to the crest
The larger the amplitude the more energy a wave has

18. Wave properties
Wavelength distance between two identical points on a wave
The shorter the wavelength the more energy it carries

19. Wave properties An ideal transverse wave has the shape of a sine curve
Sound waves’ wavelengths are difficult to find because of their odd shapes
When calculating wave length in an equation it is represented by the greek letter lambda
Wave length is measured in meters

20. Period
Period is a measurement of the time it takes for a wave to pass a given point
In a equation period is represented by the letter “T”
SI unit is seconds

22. Frequency
Frequency the number of wavelengths that pass a point in a given time
The symbol for frequency is “f”
The SI unit is hertz
1 hertz is equal to 1 vibration in 1 second

23. Wave speed
SI units is m/s

24. Wave speed

25. Speed of waves
Sound waves travel so quickly through air that we do not notice the time delay between the sound made and us hearing the sound
Sound travels faster through water (3 to 4 times faster)
Sound travels 15 to 20 times faster on a solid surface such as a metal
The speed of a wave depends on the medium it is passing through

26. Speed of sound waves Kinetic theory determines how fast waves move
Sound moving through air is moving through a gas which means that the particles are far apart and it takes longer for the particles to collide together and connect the wave to the next particle
Liquids have particles closer together and take less time
However, solid particles are so closely packed together it takes very little time for the particles to communicate the wave between each other

27. Light Light does take time to travel from place to place
The speed that light travels is known as the speed of light
The speed of light in empty space is equal to 3.00 x 108
This constant is represented by the symbol “c”
Light passes slower through a medium than empty space

28. Light
We are able to see light with frequencies of 4.3 x 1014 Hz to 7.5 x 1014 Hz
The light we can see is known as visible light
Each color has its own frequency which gives it the color we are able to see
Frequency x wavelength = speed of light

30. Doppler Effect The closer you are to a sound the louder the sound is
The pitch changes depending on the frequency of the sound
Higher pitches have a high frequency
Distance from you and the sound source can change the frequency which changes the pitch that we hear
The closer we are to the sound the higher pitch that it has

31. Reflection
Reflection the bouncing back of a wave when it meets a surface or boundary

32. Diffraction
Diffraction a change in direction of a wave when the wave finds an obstacle or an edge
If you walk past a door and can hear voices inside talking their voices are diffracting through the door and edges in the room to your ear to be heard
Depending on what objects the wave diffracts from determines how well you can hear the sound waves

34. Refraction
Refraction the bending of a wave as they pass from one medium to another
The part of the straw under the water has a different medium so it changes the angle of refraction

35. Interference
Waves can share space with other waves, unlike human bodies
Interference when several waves are in the same location, they combine to produce a single, new wave that is different from the original wave
Once the wave passes the other particles will return to their original state

36. Con vs. De Constructive Interference Destructive Interference
When two or more waves combine together and increases their amplitude
A wave of 3 cm meets a wave of 4 cm
The new wave has an amplitude of 7 cm
When two or more waves hit each other and they work against each other to decrease their amplitude
A 3 cm wave meets a 4 cm wave
Forms a 1 cm wave

37. Interference

38. Interference
If you use two tuning forks with different frequencies you create a beat
Each wave reaches your ear at a different time which change the sound of the beat
The alternating loud and soft sounds from different frequencies help create beats

39. Standing waves
Standing waves results from interference between a wave and its reflected wave