1. Module 2
Waves

2. 9-1 – The Nature of Waves
• Waves Defined • Wave – • Ex: • Waves and Energy • Waves transfer energy, not matter

3. 9-1 – The Nature of Waves
A medium is a substance or material which carries the wave.
Electromagnetic Waves are the exception, they do not need a medium to travel.

4. 9-1 – The Nature of Waves • Mechanical Waves • Transverse Waves • Ex:
• Longitudinal Waves

5. 9-2 – Wave Properties
• Parts of a Wave

6. 9-2 – Wave Properties
• Wavelength • Wavelength –

7. 9-2 – Wave Properties
• Wavelength and Frequency • Inverse relationship

8. 9-2 – Wave Properties Calculating Frequency
Frequency (Hz) = # of waves
time (s)
Calculating Wavelength
Wavelength= 1/ frequency

9. 9-2 – Wave Properties Calculating Frequency
Calculate the frequency of this wave if it occurs over 2.5 seconds.
Calculate the frequency of this wave if it occurs over 2.5 seconds.
Calculate the frequency of this wave if it occurs over 2.5 seconds.

10. 9-2 – Wave Properties Calculating Frequency
A ruby-throated hummingbird beats its wings at a rate of about 70 wing beats per second.What is the frequency in Hertz of the sound wave?

11. 9-2 – Wave Properties Calculating Frequency
Joe counts waves as they pass a lighthouse. If he counts 15 waves occurring over 4.1 seconds, what is the frequency of the waves?

12. 9-2 – Wave Properties Calculating Frequency
A buoy bobs up and down in the ocean. The waves have a wavelength of 2.5 m, and they pass the buoy at a speed of 4.0 m/s. What is the frequency of the waves?

13. 9-2 – Wave Properties Calculating Speed V = f
Velocity (m/s) = frequency (Hz) x wavelength (m)

14. 9-2 – Wave Properties Calculating Speed
A wave traveling in the water has a
frequency of 250 Hz and a
wavelength of 6.0 m. What is the
speed of the wave?

15. 9-2 – Wave Properties Calculating Speed
The lowest pitch that the average human can hear has a frequency of
20.0 Hz. If sound with this frequency travels through air with a speed
of 331 m/s, what is its wavelength?

16. 9-2 – Wave Properties Calculating Speed
A ship anchored at sea is rocked by waves that have crests 14 m apart.
The waves travel at 7.0 m/s. How often do the wave crests reach the
ship?

17. 9-2 – Wave Properties
Ocean Waves are a transverse and longitudinal wave in one
Acts as both:

18. 9-2 – Wave Properties • Amplitude • Amplitude –
• Tells about the energy of a wave

19. Ch 10 - Sound
• What causes sound? • Vibrations,Create longitudinal waves • Energy from wave transferred to your eardrum • Your brain interprets this as sound

20. Ch 10 - Sound
• Frequency of sound wave determines pitch (high, low)

21. Ch 10 - Sound • Instruments create different pitches in different ways
• Change length of instrument’s tube by opening holes (wind instruments)
• Change length of vibrating string (guitar, violin)

22. Ch 10 - Sound • Speakers turn electrical energy into sound waves
• Vibrating cone inside speaker produce sound waves

23. Ch 10 - Sound • Radio waves are used in radios.
• AM radio waves are measured in kilohertz (kHz)
• FM radio waves are measured in megahertz (MHz)
• Cell phones operate in gigahertz (GHz)

24. Ch 10 - Sound • We cannot hear sound in outer space.
• Sound waves need particles in a solid, liquid, or gas to vibrate
• No air in outer space for sound waves to vibrate.

25. Ch 10 - Sound • Speed of Sound depends on • Wind conditions
• Temperature
• Humidity
• How fast does sound travel?
• 330 meters per second (dry air, 00C)
• Faster in liquids (4x faster)
• Even faster in solids (15x faster)

26. Ch 10 - Sound • Frequency and pitch have a direct relationship
• Amplitude and loudness have a direct relationship

27. Ch 10 - Sound • The Doppler Effect
• Perceived change in wavelength, frequency, and pitch due to a moving object
• No actual change in sound, just perceived change due to the object moving toward you, then away from you.

28. Ch 10 - Sound
• Refraction of Sound • Bending of wave due to speeding up or slowing down • Change in Medium

29. Ch 10 - Sound • Reflection of Sound Waves(Sound waves bouncing)
• Waves reflect at the same angle that the wave hits (law of reflection)
• Echoes work on this principle.
• Theaters and concert halls are designed to reduce echoes.

30. Ch 10 - Sound • Applications of Reflected Waves
• Sonar “sound navigation ranging”
• Sonography
• Ultrasound
• Echolocation

31. Ch 10 - Sound Sound Waves Electromagnetic Waves
Cannot travel in a vacuum
Particles compress and relax as the wave travels through
Are longitudinal waves that transmit energy
Produce vibrations which can be sensed and some heard
Can travel in a vacuum
Have a dual quality (particles and energy)
Are transverse waves that transmit energy
Only portion of electromagnetic waves are visible
Have crests, troughs, and a resting equillibrium
Reflect, refract, and are absorbed

32. Electromagnetic Spectrum- Visible
• Electromagnetic Waves
• Are part magnetic field and part electric field
• Have properties of both waves and particles
• Can travel without a medium
• All travel at the same speed (speed of light)

33. Electromagnetic Spectrum- Visible
• Organizes electromagnetic waves according to frequency
• Also shows the wavelength of various waves
• Remember relationship between frequency and wavelength
• We can only see one small portion of the EM spectrum

34. Electromagnetic Spectrum- Visible

35. Electromagnetic Spectrum- Visible
• Visible Spectrum
• Filters allow certain colors to pass, block others

36. Electromagnetic Spectrum- Visible
• Visible Spectrum
• We see colors based on those absorbed and those reflected
• Red car = Red light reflected
• White car = all colors reflected
• Black car = all colors absorbed

37. Electromagnetic Spectrum- Visible
• Visible Spectrum • Opaque objects • Reflect the light • Cannot see through opaque items

38. Electromagnetic Spectrum- Visible
• Visible Spectrum
• Translucent objects
• Reflect some light, transmits some light
• Can somewhat see through translucent items

39. Electromagnetic Spectrum- Visible
• Visible Spectrum • Transparent objects • Transmits light • Can see through transparent items

40. Electromagnetic Spectrum- Non-Visible
• Rest of the Electromagnetic Spectrum (excluding visible light)

41. Electromagnetic Spectrum- Non-Visible
• Radio Waves • Lowest-energy, lowest frequency, largest wavelength • Transmit radio, tv, and cellular signals • Sources: electric circuits

42. Electromagnetic Spectrum- Non-Visible
• Microwave Waves • Lower-energy, lower frequency, larger wavelength • Used to heat food, used in radar guns • Sources: special vacuum tubes, like those in microwave ovens

43. Electromagnetic Spectrum- Non-Visible
• Infrared Waves
• Low-energy, low frequency, large wavelength
• Heat emitted from warm objects, used in special cameras
• Sources: anything that gives off heat

44. Electromagnetic Spectrum- Non-Visible
• Ultraviolet (UV) Waves • high-energy, high frequency, small wavelength • Emitted from the sun, very hot objects, like sun lamps • Sources: special vacuum tubes, like those in microwave ovens

45. Electromagnetic Spectrum- Non-Visible
• X-ray Waves
• higher-energy, higher frequency, smaller wavelength
• Emitted from x-ray machines, used to image people’s bones
• Detected through high speed collisions between electrons

46. Electromagnetic Spectrum- Non-Visible
• Gamma Ray Waves
• highest-energy, highest frequency, smallest wavelength
• Emitted from nuclear reactions
• Sources: radioactive substances
• Can be detected with a Geiger counter.