1. EMS & Sound
Unit 6 – Lecture 2

2. EM Waves do not require a medium
work by vibrating electric & magnetic fields

4. Electromagnetic Spectrum

5. The Electromagnetic Spectrum
Radio Waves – carry information
radios am fm
televisions
MRI
cell phones & cell phone towers

6. The Electromagnetic Spectrum
Microwaves
microwave oven
Doppler radar [weather detection]
other radar

7. The Electromagnetic Spectrum
Infrared
heat [thermal energy]
remote controls
heating lamps for food

8. The Electromagnetic Spectrum
Infrared
picked up by night vision goggles
thermal imagery
some animals can see in infrared [rattlesnakes]

9. The Electromagnetic Spectrum
Visible Light
light bulb…etc.
a prism –  separates “white “ light into its colors

10. The Electromagnetic Spectrum
Ultraviolet UV waves
from sun and other stars
helps us make vitamin D
kill bacteria on food [damage cells]
fluorescent materials glow [black light]
can be seen by some animals [birds, bees]

12. The Electromagnetic Spectrum
X-rays
medical appliations
airport screening

13. The Electromagnetic Spectrum
Gamma Rays
radioactive [unit 3!]
E emitted from nucleus
medical applications
radiation therapy
sterilization
used to look at stars

14. X-Rays

15. Sound Important Sound Terms: Decibel – unit of sound intensity
Ultrasonic – above 20,000 hertz
Echolocation – using reflected waves to judge the size, shape, or location of an object
Supersonic – faster than the speed of sound
Vibration – cause of sound

16. Sound caused by vibrations composed of compressional waves
in turn this vibrates your ear drum to send signals to your brain
waves must have a medium through which to travel

17. Sound

18. Sound
speed of sound is determined by the medium through which it travels
type of medium
state of matter
solids, liquids, gases
closer the particles, faster the travel of sound
temperature of the medium
increased temperature, increased sound
this change of speed distorts the sound

19. The Doppler Effect
the change in pitch and frequency due to a moving wave source
reason why the same thing sounds different as it approaches you or moves farther away
higher as approaching
lower as moving away

20. The Doppler Effect basically…
imagine you’re throwing cheese-balls at someone at regular intervals. [constant frequency]
if you stay in the same place, each ball hits your victim at the same interval [frequency] at which you’re throwing it.

21. The Doppler Effect basically…
now, if you start running toward your victim, the distance between you and the person keeps getting smaller
because the distance is smaller, the cheese-balls are hitting the victim more quickly [with a higher frequency]
this is why the pitch gets higher as the object approaches.

22. The Doppler Effect basically… …but to you, the frequency is the same
this is how the sound seems to the person who’s in the car. [it remains the same]

23. The Doppler Effect basically…
as you run, you keep throwing the cheese-balls at the same frequency
…but as you get further, it takes more time for each cheese- ball to reach your victim.
they are being pelted with cheese-balls less often [lower frequency]
this is why the pitch gets lower as the object moves farther away

24. The Doppler Effect In the story… what represented the frequency?
what represented the sound waves?
What would display the doppler effect moreso:
a race car passing
a police siren

25. Speed Equations Speed of Sound speed = distance / time v = d / t
Speed of Waves
speed = wavelength * frequency
v = λ * f

26. Homework New worksheet – Speed of Sound Problems
ALSO – work on your packet unless
it’s finished
because it’s finished you’re willing to show it to me and turn it in for collection early.