1. Labs and Activities for this Presentation:
NOTE:
This presentation was not made for public use. Please do not use this presentation without my permission and the permission of each of the authors of the photographs, quotes, and other materials that they contain.
Thank you,
Vicki Hughes
Labs and Activities for this Presentation:
Prism Demo

2. wAVES

3. WAVES OF SOUND AND LIGHT
Electromagnetic Waves = can travel through a vacuum
Example: light waves
Mechanical Waves = must have a medium to travel in
Example: sound waves

4. Characteristics of Waves
Crest = top of a wave
Trough = bottom of a wave Wavelength is the distance from crest to crest

5. Characteristics of Waves
Amplitude is the distance from resting to the top or bottom of a wave.
amplitude
rest
amplitude

6. Characteristics of Waves
Frequency is the number of waves that pass a fixed point in a given amount of time. 3 4 2 1 5
seconds

7. Properties of Waves Wave Speed = Wavelength x Frequency
The speed of a wave is a product of its wavelength and frequency.
What is the formula for Wave Speed?
Wave Speed = Wavelength x Frequency
What is the formula for Frequency?
Wave Frequency = Speed Wavelength

8. Properties of Electromagnetic Waves
Example Problem: An electromagnetic wave has a wavelength of 3 meters and a speed of 3.0 x 108 m/s. What is its frequency?
Wave Frequency = Speed Wavelength
Wave Frequency = 3.0 x 108 m/s = 1. 0 x 108 Hz m

9. Transverse waves = move perpendicular to the path of travel.
Types of Waves
Transverse waves = move perpendicular to the path of travel.
perpendicular
Longitudinal Wave
Longitudinal waves = move parallel to the path of travel.
parallel

10. Sound is Mechanical
Remember, mechanical waves must have a medium through which they move.
This medium can be solid…

11. Sound is Mechanical
This medium can be liquid…

12. Light & Sound
This medium can be gaseous…

13. If a tree falls in the forest and nobody is around to hear it, does it make a sound?

14. Characteristics of Sound
All sounds begin with vibrating matter.

15. Characteristics of Sound
Ear captures vibrations.
How do we hear sounds?
Guitar string vibrates.
Vibration is transferred to air particles and move away from the string in waves.
Auditory Transduction 6:44

16. Characteristics of Sound
Remember, sounds cannot travel through space…because there is no medium.

17. Characteristics of Sound
Properties of Sound: SPEED
Speed of Sound = the distance that sound travels in a given amount of time.
Sound travels more slowly than light.
BOOM!

18. Characteristics of Sound
Sounds travels faster in liquids than in gases… and faster in solids than in liquids.

19. Characteristics of Sound
Loudness is determined by sound intensity.
Intensity is a measure of the amount of energy in sound waves.
Unit of intensity = decibel (dB)

20. Characteristics of Sound
Pitch of Sound = how high or low a sound seems to a listener.
Waves and Pitch 2:00

21. Characteristics of Sound
Pitch depends on the frequency of sounds.
Frequency = how often something happens
The frequency of waves is the number of waves that pass a fixed point in a given amount of time.

22. Characteristics of Sound
Unit for frequency = hertz (Hz)
Humans can hear frequencies between 20 – 20,000 Hz.

23. Characteristics of Sound
Doppler Effect = change in frequency when sound waves are moving.
Example: As a train approaches it becomes louder and louder, then as it leaves you it becomes softer and softer.

24. Electromagnetic Waves
Electromagnetic radiation is the transfer of energy by waves traveling through matter or across empty space.
Electromagnetic waves consist of vibrating electric and magnetic fields.

25. Electromagnetic Waves
ACT L18
Electromagnetic waves do NOT require a medium…
So electromagnetic waves can travel through space.

26. Behavior of Waves
Electromagnetic waves can also travel through matter just like mechanical waves.
They can:
Reflect (bounce back)
This property is called
reflection.

27. Electromagnetic Waves
Electromagnetic waves travel through matter just like mechanical waves.
They can:
Refract (bend through objects)
This property is called refraction.
Light through a prism 3:22
Demo: Prism

28. Electromagnetic Waves
Electromagnetic waves travel through matter just like mechanical waves.
They can:
Diffract (bend around objects)
This property is called diffraction.

29. Electromagnetic Waves
Electromagnetic waves travel through matter just like mechanical waves.
They can:
be transmitted (sent from one place to another)
This property is
called transmission.

30. Electromagnetic Waves
Electromagnetic waves travel through matter just like mechanical waves.
They can:
be absorbed (gathered in by an object)
This property is
called absorption.
Absorbed light

31. Electromagnetic Waves
Electromagnetic waves travel through matter just like mechanical waves.
They can:
scatter (deviate from their
original path)
This property is
called scattering.

32. Electromagnetic Waves
Electromagnetic waves act like waves most of the time,
But sometimes…They act like particles!

33. Electromagnetic Waves
Photon = energy released when electromagnetic radiation acts like particles and drops to a lower atomic level.

34. Electromagnetic Waves
The amount of energy in a photon depends on the frequency of the electromagnetic wave that produced it.

35. Types of Electromagnetic Waves
Electromagnetic Spectrum is the full range of wavelengths.

36. Types of Electromagnetic Waves
Radio Waves
lowest frequencies
used for radio and television broadcasts, microwave ovens, cell phone transmissions, and radar

37. Types of Electromagnetic Waves
Light Waves
Includes visible light, infrared light, and ultraviolet light. UV
infrared
Visible Light

38. Types of Electromagnetic Waves
Light Waves can be separated using a triangular prism.

39. Types of Electromagnetic Waves
Visible Light
The only light that humans can see.
Visible Light

40. Any Questions? ACT L19 only #1 and #3. EOG CH 2 Review
Light Drawing