2. Mechanical and Electromagnetic
What is a Wave?
It’s a disturbance that propagates
through a material/medium or through space.
Waves transfer energy without
transporting lots of matter.
Two types:
Mechanical and Electromagnetic

3. What is a Wave?
It’s a disturbance that propagates
through a material/medium or through space.
In order for a mechanical wave to start, energy first has to create a disturbance in an elastic (movable) medium, like air, water, oil, etc.

4. BUT…no medium is needed for ELECTROMAGNETIC (EM) waves.
Light, radio, x-rays, and gamma rays
are some examples of EM waves.

5. All EM waves travel through empty
space (a vacuum) at a speed of approximately
3.00 x 108 m/s or 186,000 miles/sec.
This speed is known as the speed of light.

6. Like a Slinky
Like a Jump Rope

7. TRANSVERSE LONGITUDINAL
The displacement of the particles
of the medium is perpendicular to
the direction of wave propagation.
LONGITUDINAL
The displacement of the particles
of the medium is parallel to the
direction of wave propagation.

8. SURFACE A combination of transverse and longitudinal.
Click here, here, and here
to view simulations of
transverse and longitudinal waves.

9. the maximum displacement of a particle of the medium from
Amplitude
the maximum displacement
of a particle of the medium from
the rest or equilibrium position
Often labeled “A,”and measured in units of length

10. In sound waves, amplitude corresponds to volume or loudness.

11. related to the position and motion of the particles of the medium
Phase
related to the position and motion
of the particles of the medium

12. the shortest distance between two points that are “in phase”
Wavelength
the shortest distance between
two points that are “in phase”
Labeled as l and measured in units of length

13. Frequency - the number of complete waves that pass a point per unit time
denoted by f and measured in units of Hz
Period - the shortest time interval during
which the motion of the wave repeats itself
denoted by T and measured in units of time
T = 1/f
&
f = 1/T

14. If you are solving wave problems that include the word “period,” you will have to use one of the two formulas below.
Two-step solution.
T = 1/f OR
f = 1/T

15. In the world of sound waves, frequency corresponds to pitch.

16. v = d/t = l/T = f l Velocity - the speed of the wave
denoted by v and measured in units of dist/time
The speed of a wave depends on the properties
of the medium through which it is traveling.
v = d/t = l/T = f l

18. Reflection the turning back of a wave when
it reaches the boundary of the
medium through which it is traveling

19. Law of Reflection
the angle of incidence (relative to the “normal” line is equal
to the angle of reflection

20. Refraction
the bending of a wave as it passes at an angle from one medium into another of density (“refractive index”)
For refraction to occur, the wave
must change speed in the new medium.

21. Interference
This happens when two or more waves pass through a medium at the same time.
The displacements caused by each wave are added together.

22. results in a larger amplitude results in a smaller amplitude
2 Types of Interference
Constructive
results in a larger amplitude
Destructive
results in a smaller amplitude

23. Read more about interference here. Click here to view the interference
pattern resulting from the superposition
of two transverse waves.
Click here and here to view
simulations of the interference of
two circular waves.

24. Waves in Communication
Communicate:
to ‘share or exchange information, news, or ideas’
Communications: ‘the means of connection between people and places’

25. Waves in Communication
Can be speech, text, images or any form of data
s or teleconferencing using satellite communication, cellular phones, pagers, and so on

26. Waves in Communication
Transmitted as
voltage or current through wires,
radio emissions through the air,
pulses of light through optical fibers.
Transmissions can be thought of as ‘electromagnetic waves in communication systems’

27. Waves in Communication
Radio stations broadcast on different frequency ranges.
Amplitude Modulation (AM) radio broadcasts and
Frequency Modulation (FM) radio broadcasts.

28. Waves in Communication
Cell phones usually transmit signals in the 900 MHz or 1.8 GHz band
“M” = 1 million
“G” = 1 billion
“Hz” = Hertz = cycles/second
FM radio broadcasts use the 88 MHz to 108 MHz band.

29. Digital and Analog signals
Radio waves, microwaves, infrared radiation and light are the parts of the EM spectrum used for communication.
There are two types of signal used: analog and digital.

30. Digital and Analog Signals
An analog signal is always changing according to frequency and amplitude changes in the voice or music being transmitted.
A digital signal has just two values – which we can represent as 0 and 1.
Binary – two numbers

31. Digital and analog signals

32. The voice, music or data is converted into 0s and 1s.
The signal becomes a stream of 0 and 1 values.
Added to the EM wave and transmitted.
Signal is received and then decoded to recover the original signal.

33. In communication systems, information can be sent in a one-way or a two-way direction.
Called either a simplex system or duplex system.

34. Simplex System Duplex System
Information can only be transmitted in a one-way direction, as in television and radio broadcasting
Duplex System
Information can be transmitted in both directions, such as with a cell phone.

36. Wireless Communication Technology
No cables or wires. Info transmitted through air using EM waves
The tech includes such things as smart phones, computers, laptops, Bluetooth Technology, printers, GPS, Wi-Fi, dish TV, radio…

37. Satellite Communication
The signal is a modulated microwave beam
Beam sent to satellite, which amplifies the signal and sends it back to an antenna on Earth

38. Infrared Communication
Transmitter: photo LED
Receptor: photo diode
The invisible IR information signal transmitted from source to target is captured and saved there by the photoreceptor.
Mobile phones, remotes, TVs, security systems, laptops etc.

39. How do you make a radio wave?
Inside the transmitter, a pulsed electrical current, DC (one direction), is sent through a wire
The creates a changing EM field around the wire.
This field sends a wave outward from the wire.
The wave carries a coded signal, translated by the receiver

40. A.M. Stands for Amplitude Modulation.
Information is put into a radio wave by varying the amplitude of the current
To was send 1's and 0's, could have just two different levels of amplitude that correspond to these numbers--1 being high, 0 being low            

42. F.M. Stands for frequency modulation.
Wave amplitude is kept constant, but frequency is varied
               

44. Other kinds of electromagnetic radiation, including radio waves, are made by natural processes such as the nuclear reactions in a star.