1. Waves & Sound I. Characteristics of Waves Waves Transverse waves
Longitudinal waves
Measuring waves

2. A. Waves
Waves
rhythmic disturbances that carry energy through matter or space
Medium
material through which a wave transfers energy
solid, liquid, gas, or combination
electromagnetic waves don’t need a medium (e.g. visible light)

3. B. Waves & Energy Waves Energy Carry energy Waves carry energy
Waves are caused by vibrations
Can do work
Move objects
Energy
Waves carry energy
Vibration is a transfer of energy
As waves carry energy the particles in the medium move
the direction of the motion determines the type of wave

4. Electromagnetic Waves
C. Categories of Waves
Mechanical Waves
Must travel through a medium
Cannot travel through a vacuum
Examples: sound, ocean waves
Electromagnetic Waves
Does not require a medium
Can be transferred through a vacuum
Examples: light, UV rays, Visible light

5. D. Types of Waves
Two Types:
Longitudinal Transverse

6. D. Transverse Waves Transverse Waves
medium vibrates perpendicular to the direction of wave motion
Examples: water waves, electromagnetic waves

7. corresponds to the amount of energy carried by the wave
B. Transverse Waves
Wave Vocabulary
corresponds to the amount of energy carried by the wave
crests
wavelength
amplitude
nodes
troughs

8. E. Longitudinal Waves Longitudinal Waves (a.k.a. compressional waves)
medium moves in the same direction as the wave’s motion
Examples: sound waves, springs, slinky

9. E. Longitudinal Waves Wave Anatomy compression wavelength rarefaction
Amount of compression corresponds to amount of energy ≈ AMPLITUDE

10. F. Measuring Waves Frequency ( f )
# of waves passing a point in 1 second
SI unit: Hertz (Hz)
1 second
shorter wavelength ⇒ higher frequency ⇒ higher energy

11. v = λ × f F. Measuring Waves Velocity ( v )
speed of a wave as it moves forward
depends on wave type and medium
v = λ × f
v: velocity (m/s)
λ: wavelength (m)
f: frequency (Hz)

12. F. Measuring Waves Solid Liquid
Molecules are close together so waves travel very quickly.
Molecules are farther apart but can slide past one another so waves do not travel as fast.
Gas
Molecules are very far apart so a molecule has to travel far before it hits another molecule, so waves travel slowest in gases.

13. F. Measuring Waves
EX: Find the velocity of a wave in a wave pool if its wavelength is 3.2 m and its frequency is 0.60 Hz.

14. F. Measuring Waves
EX: An earthquake produces a wave that has a wavelength of 417 m and travels at 5000 m/s. What is its frequency?

15. Wave Interactions Wave Interaction
When a wave meets an object or another wave.
When a wave passes into another medium
Examples: reflection, diffraction, refraction, interference, resonance

16. Reflection Reflection when a wave strikes an object and bounces off
Normal
Reflection
when a wave strikes an object and bounces off
incident beam
reflected beam

17. Reflection
When a wave bounces off a surface that it cannot pass through

18. Refraction Refraction
bending of waves when passing from one medium to another
caused by a change in speed
slower ⇒ light bends toward the normal
SLOWER
FASTER
faster ⇒ light bends away from the normal

19. Refraction
The bending of a wave as it enters a new medium at an angle.

20. Refraction
Refraction depends on…
speed of light in the medium

21. Refraction
Example:
View explanation.

22. Diffraction
The bending of a wave as it moves around an obstacle or passes through a narrow opening.

23. Diffraction Diffraction bending of waves around a barrier
longer wavelengths (red) bend more - opposite of refraction

24. A. Speed of Sound 344 m/s in air at 20°C Depends on: Type of medium
travels better through solids than through liquids
can’t travel through a vacuum
Temperature of medium
travels faster at higher temperatures

25. converted to nerve impulses in cochlea
B. Human Hearing
sound wave
vibrates ear drum
amplified by bones
converted to nerve impulses in cochlea

26. B. Human Hearing Pitch highness or lowness of a sound
depends on frequency of sound wave
human range: ,000 Hz
ultrasonic waves
subsonic waves

27. B. Human Hearing Intensity volume of sound
depends on energy (amplitude) of sound wave
measured in decibels (dB)

28. B. Human Hearing
DECIBEL SCALE
120
110
100 80 70 40 18 10

29. A. Electromagnetic Radiation
transverse waves produced by the motion of electrically charged particles
does not require a medium
speed in a vacuum = 300,000 km/s

30. B. Electromagnetic Spectrum
The full range of light

31. B. Electromagnetic (EM) Spectrum
long λ
low f
low energy
short λ
high f
high energy

32. C. Types of EM Radiation
Rabbits Meet In Very Unusual Xciting Gardens

33. C. Types of EM Radiation Radio waves Lowest energy EM radiation
FM - frequency modulation
AM - amplitude modulation
Microwaves
penetrate food and vibrate water & fat molecules to produce thermal energy

34. C. Types of EM Radiation Infrared Radiation (IR)
slightly lower energy than visible light
can raise the thermal energy of objects
thermogram - image made by detecting IR radiation

35. C. Types of EM Radiation Visible Light
small part of the spectrum we can see
ROY G. BIV - colors in order of increasing energy R O Y G. B I V
red
orange
yellow
green
blue
indigo
violet

36. C. Types of EM Radiation Ultraviolet Radiation (UV)
slightly higher energy than visible light
Types:
UVA - tanning, wrinkles
UVB - sunburn, cancer
UVC - most harmful, sterilization

37. C. Types of EM Radiation Ultraviolet Radiation (UV)
Ozone layer depletion = UV exposure!

38. C. Types of EM Radiation X rays higher energy than UV
can penetrate soft tissue, but not bones

39. Radiation treatment using radioactive cobalt-60.
C. Types of EM Radiation
Gamma rays
highest energy on the EM spectrum
emitted by radioactive atoms
used to kill cancerous cells
Radiation treatment using radioactive cobalt-60.