1. Waves

2. Waves A wave is an oscillation that travels from one place to another.
The word oscillation means a motion that repeats regularly.
The surface of the water oscillates in response to the ball being poked and the oscillation spreads outward from where it started.
An oscillation that travels is a wave.

3. Waves
Waves carry information and energy and waves spread through connections
Think of a string
Radio waves carry television signals
Microwaves carry cellphone
conversations or facebook/twitter/instagram/ snapchat updates
(aka WHAT REALLY MATTERS!!!)

4. Waves Two types of waves Mechanical Waves Electromagnetic waves
Need a medium to travel through
Ex. Sound, water
Electromagnetic waves
Do not need a medium to travel through
Ex. Light, radio

5. Waves have two shapes Longitudinal Transverse

6. Waves Longitudinal Waves (compression waves)
Moves parallel to the wave motion
Sound waves are longitudinal waves

7. Parts of A Longitudinal Wave
•Compression -compact area of wave
•Rarefaction -less dense area of compression Wave
1Wavelength=1compression+1rarefraction

8. Transverse Waves Moves perpendicular to the direction the wave moves

9. Parts of a transverse wave
•Crest -highest point of wave
•Trough -lowest point of wave
•Wavelength -distance between one point in a
wave and the exact point on the next wave.
•Amplitude -distance from crest or trough to middle

11. Waves
We use the Greek letter “lambda” to represent wavelength. A lambda (λ)
looks like an upside down “y.”

12. Waves Frequency In an oscillator, frequency is the number
of cycles it makes per second
The unit of measurement is hertz (Hz)
A frequency of one cycle per one
second is one hertz

13. Harmonic Motion Period
Is the length of time for one cycle; how long it takes for one repetition

14. Harmonic Motion
Frequency and period are inversely related. The period is the time per cycle. The frequency is the number of cycles per time.

15. Speed
The speed of a wave describes how fast the wave can transmit an oscillation one place to another.
Waves can have a wide range of speeds:
Most water waves are slow (1-2 mph)
Sound waves move ~660 mph
Light waves are extremely fast 
186,000 miles per second

16. Waves Speed is frequency times wavelength
In one complete cycle, a wave moves
moves forward one wavelength.

17. The wavelength for a wave is 0. 5 meter, and its frequency is 40 hertz
The wavelength for a wave is 0.5 meter, and its frequency is 40 hertz. What is the speed of this wave?
speed = 40 Hz × 0.5 m = 40 (1/sec) × 0.5 m
speed = 20 m/sec
The speed of the wave is 20 m/sec.

18. Waves in Motion In what shapes do we find waves?
What happens when a wave hits something?
We will start with waves in water as they are easy to make and observe.
Every process we see with water waves also occurs with sound and light waves.

19. In water waves, crests are also called wave fronts.
Waves in Motion
In water waves, crests are also called wave fronts.

20. Plane Waves And Circular Waves
The crest of a plane wave is a straight line
It is started by disturbing the water in a line
It moves perpendicular to the wave fronts
Circular Waves
Crests of circular waves are circles
They are started by disturbing the water
at a single point
Circular waves radiate outward from the
center

21. Waves in Motion

22. Wave Interactions Four types of interactions Reflection Refraction
Wave interactions are when waves interact with an object or another wave
Four types of interactions
Reflection
Refraction
Diffraction
Absorption

23. Reflection
Reflection – bouncing back of a wave after it strikes a barrier
Angle of incidence = angle of reflection

24. Refraction
Refraction – bending of a wave as it moves from one medium to another
Medium changes - wave passes from one medium to another (solid to gas, liquid to solid etc)
The speed of the wave changes as it moves into medium
of different density and causes wave to bend)
Speed is affected by density of the medium.

25. Diffraction
Diffraction – The bending of a wave as a result of the interaction between a wave and the edge of an object
Examples:
Waves bend around a rock in the ocean
Waves bend around your legs when you stand in the surf at the beach and come together after they pass your legs

26. Waves in Motion Absorption
When the amplitude of a wave gets smaller and smaller as it passes through a material
The wave energy is transferred to the
absorbing material.

27. Amplitude changes, speed and frequency do not
Interference
Interference – effect of two or more waves intersecting
wave-wave interaction or wave overlap
It’s what happens when waves meet
Amplitude changes, speed and frequency do not

28. Constructive Interference
resulting wave gets bigger – “additive”
energy increases
happens if both wave crests on the same side of the line of origin
two crests at the same location – amplitude of wave formed is the sum of the amplitudes

29. Destructive Interference
Resulting wave gets smaller (subtract)
Energy loss
Crest of one wave meets trough of another wave
2 possibilities: 1. single wave of reduced amplitude OR 2. no wave at all
If crest and troughs are equal but opposite – result is no wave at all (cancel each other out)

31. http://www. aplusphysics

32. Doppler Effect
Doppler effect is the change in frequency of a wave for an observer moving relative to its source.

33. Resting Sound Source Frequency fs V=340m/s Frequency fo source at rest
observer
at rest

34. Sound source moving toward observer
Observer hears
increased pitch
(shorter wave length)
Frequency fs
source
observer
at rest

35. Sound source moving away from observer
Observer hears
decreased pitch
(longer wave length)
Frequency fs
observer
at rest
source

36. BIG BANG THEORY