1. Wave Basics
Unit 9 – Lecture 1

2. Waves rhythmic disturbances which transmit energy
through a medium [substance – solid, liquid, or gas]
ex: light & sound [note: sound and other types of waves can carry information in the form of energy]

3. Waves
Cord Demo – does the cord itself move from place to place? is it traveling with the wave?
Waves move through the medium – they do not move the medium itself.
like the wave at a sporting event

4. Types of Waves Mechanical waves – need to travel through matter
transverse waves
compressional [aka longitudinal]
Water waves move in a combination of these movements

5. Transverse Waves Transverse waves
matter in medium moves back and forth at right angles to the wave’s energy
Electromagnetic rays travel in transverse waves
if wave is traveling L or R, the movement of the medium is up and down.
if wave is traveling up or down, the movement of the medium is L & R

6. Transverse Waves Parts of a Transverse Wave
draw this wave on your paper in the space provided.

7. Transverse Waves Parts of a Transverse Wave crest
the highest point of the wave – highest E
there can be many crests

8. Transverse Waves Parts of a Transverse Wave trough
the lowest point of the wave – lowest E
there can be many troughs

9. Transverse Waves Parts of a Transverse Wave resting position
does not have to be at zero!

10. Transverse Waves Parts of a Transverse Wave amplitude
the furthest distance from the resting position
from resting position to either crest or trough

11. Transverse Waves Parts of a Transverse Wave wavelength
distance of one wave
distance between two equal points on a wave

12. Transverse Waves

13. Longitudinal Waves Longitudinal Wave [aka Compressional Wave]
matter in the medium moves back and forth along the same direction of the wave
sound and seismic waves
imagine a coil: a slinky or spring
compress coils then release, wave moves coils in a compression to other side

14. Longitudinal Waves Parts of a Longitudinal Wave
Draw a coil on your sheet like the one below, with areas of densely bound coils, and areas of lesser bound coils

15. Longitudinal Waves Parts of a Longitudinal Wave rarefaction
a non-compressed area of this type of wave
point of lowest energy

16. Longitudinal Waves Parts of a Longitudinal Wave compression
a compressed area of this type of wave
point of highest energy

17. Longitudinal Waves Parts of a Longitudinal Wave wavelength
distance of one wave
distance between two equal points on a wave

18. Longitudinal Waves

19. Transverse vs Compressional Waves
Transverse waves
Longitudinal Wave [aka Compressional Wave]

20. Practice
What is a wave?
What is the name for the material through which a wave travels?
In which kind of wave do the particles of the medium vibrate in the same direction as the wave?
What is transmitted by a wave?
In which kind of wave do the particles of the medium vibrate at right angles to the wave?
How is a crest similar to a compression / a trough similar to a rarefaction?

21. Wave Measurements
Frequency – number of waves that pass a certain point per unit of time. [waves per time]
measured in Hertz [Hz] for waves per second
as waves travel faster [higher frequency], the wavelength decreases
what type of relationship is this?
1 Hz = 1 wave per second

22. Wave Measurements
Period = time it takes to complete one cycle [time per wave]
T = t / # of waves OR
this is the inverse of frequency
T = 1/ f

23. Practice
The period of a wave is 3 seconds. What is its frequency?

24. Wave Measurements Wave Speed can depend on the medium
sound travels best through solids [particles close together] but radio waves and others can’t travel through them

25. Wave Measurements Calculating Wave Speed
recall: speed = distance / time
recall: frequency = waves/time
wave speed = wavelength * frequency
v = λ * f
does this make sense? let’s see
wave speed (m/s) = wavelength (m) * waves (#) time (s)

26. Electromagnetic Waves
Electromagnetic Waves – do not need matter to transfer energy
wave transferred by vibration of magnetic & electric fields
EMS = range of electromagnetic radiation
EMS contains Visible Light in roughly the center of spectrum R O Y G B I V

27. Electromagnetic Waves
all EM waves travel at the speed of light roughly 3 x 108 m/s or 186,282.6 miles per second
variable for speed of light = C
this is currently the fastest speed in the universe

28. Electromagnetic Spectrum

29. Electromagnetic Spectrum
How to remember?

30. Electromagnetic Spectrum
Helpful Prefixes:
mega = M = 1 x 106
nano = n = 1 x 10-9