1. Chapter 14 and 15

2. Section 1: Types of Waves
What is a Wave?
A wave is a periodic disturbance in a solid, liquid, or a gas as energy is transmitted through a medium.
A wave carries energy through matter and space.
Waves transfer Energy – can do work on objects.
Ex: seismic waves, water waves, light, sound
A medium is the physical environment (matter) in which the wave travels through.

3. Section 1: Types of Waves

4. Section 1: Types of Waves
Two Types of Waves
Mechanical Waves – a wave that requires a medium to travel.
sound
Electromagnetic Wave (EM) – a wave that does not require a medium
A wave that consists of oscillating electric and magnetic fields, which radiate outward at the speed of light.
Light waves

5. Section 1: Types of Waves
Energy may spread out as a waves travels
Most waves are caused by vibrating objects.
EM waves are caused by vibrating particles.
Mechanical waves cause particles in the medium to vibrate as the wave passes through them.

6. Section 1: Types of Waves
Vibrations involve transformations of Energy.
Pull weighted spring and store EPE then let go EPE is converted to KE and then back to EPE (GPE) and back to KE then back to EPE.
Simple harmonic motion

7. Section 1: Types of Waves

9. Section 1: Types of Waves
Connect many weighted springs together only pull the first one and can transfer energy to rest of springs.
A wave can pass through a series of vibrating objects
Damped harmonic motion

10. Section 1: Types of Waves

11. Section 1: Types of Waves
Transverse and Longitudinal Waves
Two wave forms (classes)
Based on direction the particles in the medium move as the wave passes.
1) Transverse Wave – particle motion is perpendicular to direction of the wave.
Up and down
2)Longitudenal Wave – (compressional wave) particle motion is parallel with the wave motion.
Back and forth

12. Section 1: Types of Waves

13. Section 1: Types of Waves
Surface Wave
Combination of transverse and longitudinal waves at the boundary of two mediums.
Moves particles in a circular motion.

14. Section 1: Types of Waves

15. Section 2: Characteristics of Waves
Wave Properties
Transverse waves – S shape called sine waves.
Crest – highest point
Trough – Lowest point
Amplitude – maximum distance that the particles of a wave’s medium vibrate from their rest position.
Larger the amplitude – more the energy the wave carries.
Wavelength – measures the distance b/w two equivalent parts of a wave.
Crest to crest or trough to trough

16. Section 2: Characteristics of Waves

17. Section 2: Characteristics of Waves
Longitudinal waves
Compression – crowded area of particles.
Equivalent to crest
Rarefaction – area of spaced out particles.
Equivalent to trough.
Wavelength – measures the distance b/w two equivalent parts of a wave.
Compression to compression or rarefaction to rarefaction
Amplitude of Longitudinal waves is related to how tightly the medium is pushed together at the compression

18. Section 2: Characteristics of Waves

20. Section 2: Characteristics of Waves
Wavelength represented by Greek letter Lambda or λ.
SI unit is meter.
Period – measures how long it takes for waves to pass by.
Time it takes for one full wavelength of a wave to pass a certain point.
Symbol is T
SI unit is seconds

21. Section 2: Characteristics of Waves

22. Section 2: Characteristics of Waves
Frequency – measures the rate of vibrations
# of full wavelengths that pass a point in a given time interval.
Measures how rapidly vibrations occur in the medium, at the source of the wave, or both.
Symbol is f
SI unit is the Hertz or Hz = 1/s = Waves/s

23. Section 2: Characteristics of Waves
Formula:
Frequency = 1 / period
Frequency and period are inversely proportional.

24. Section 2: Characteristics of Waves
Wave Speed
velocity = wavelength times frequency
SI unit is m/s

25. Section 2: Characteristics of Waves

27. Section 2: Characteristics of Waves
Factors that affect wave speed.
Speed of wave depends on the medium.
Kinetic Theory of Matter explains differences in wave speed.
Gases – waves do not travel fast – particles too spread out.
Liquid – molecules closer together – vibrations transfer more quickly.
Solid – waves travel very quickly – molecules most compact and energy is transferred more easily.

29. Section 2: Characteristics of Waves
Light has a finite speed
All EM waves in empty space travel at same speed.
Speed of light = 3.00 x 108 m/s
or 186,000 miles/s
Symbol is c
Moves slower in air, water, and other medium.

31. Electromagnetic Spectrum
Light comes in a wide range of wavelengths and frequency
Increase Frequency – Decrease Wavelength
Called the Electromagnetic spectrum
Frequency proportional to energy.
Higher the frequency Higher the energy.

34. Section 2: Characteristics of Waves
Doppler Effect
Pitch is determined by the frequency of sound wave.
Pitch is how high or low the sound is.
High frequency = high pitch

35. Section 2: Characteristics of Waves
Frequency changes when the source of waves is moving.
Moving toward
Wave is compressed in the direction of the wave motion.
Shortens wavelength
Higher frequency = higher pitch

36. Section 2: Characteristics of Waves
Moving away
Wavelength increases
Smaller frequency = lower pitch
Doppler Effect – observed change in frequency of a wave when the source or observer is moving.

37. Section 2: Characteristics of Waves

38. Section 3: Wave Interactions
Waves tend to travel in straight lines in a medium.
Three ways Waves interactions with barriers:
Reflection – the bouncing back of a wave when it hits a surface that it does not go through.
All types of waves can be reflected.
The angle of incidence of a wave is always equal to the angle of reflection.
Normal – an imaginary line perpendicular to a reflective surface
Angle of incidence – the angle formed by the wave striking the surface and the normal
Angle of reflection – the angle formed by the reflected wave and the normal

43. Light and Color
Seeing Color

44. Section 3: Wave Interactions
Refraction – the bending of a wave caused by a change in its speed as it moves from one medium to another
The greater the change in speed is, the more the wave bends.
When a wave passes into a material that slows it down, the wave is bent toward the normal.
When a wave passes into a material that speeds it up, the wave is bent away from the normal.

49. Section 3: Wave Interactions
Diffraction – an object causes a wave to change direction and bend around it.
Reason that shadows do not have perfectly sharp edges.

51. Section 3: Wave Interactions
Interference – the ability of two or more waves to combine and form a new wave
Waves pass right through each other and continue in their original direction.
New wave exists only while the two original waves continue to overlap.

52. Section 3: Wave Interactions
Two types of Interference
Constructive interference – waves add together
Crest of one wave overlaps the crest of another.
Destructive interference – waves subtract from each other
Trough of one wave overlaps with crest of another.

56. Section 3: Wave Interactions
Standing waves – a wave pattern that stays in one place
Form when waves of equal wavelength and amplitude that are traveling in opposite directions continuously interfere with each other.
Nodes – the places where two waves always cancel each other
Antinodes – area of maximum vibration