1. Electromagnetic Waves

2. Electromagnetic Waves – waves that DO NOT need a medium to travel and carry energy; they can travel through a vacuum (empty space)
Examples of EM waves:
Radio waves – GPS, MRI, RADAR
Microwaves – heating up food
Infrared waves – heat lamps, warmth
Visible Light – what we can see
Ultraviolet rays (UV) – causes cancer and vitamin D
X-rays – too much exposure can cause cancer
Gamma rays – radiation, hulk, nuclear weapons

3. EM Waves
ALL EM waves travel at the speed of light (VERY FAST) which is 3 x 108 [m/s] (300,000,000 [m/s]) or 671,224,363 mph.
At this speed, they can travel around the world 8 times in one second

4. EM Spectrum
EM Spectrum – range of EM waves from low to high frequency

5. EM Spectrum

6. Longest wavelength Lowest frequency
EM Spectrum
Longest wavelength Lowest frequency
Shortest wavelength
Highest frequency

7. Visible Light
Visible Light – The part of the EM spectrum that humans can see; from 700 [nm] to 390 [nm]

8. Long wavelength Low frequency Low energy COLD
R O Y G B I V
Long wavelength Low frequency Low energy COLD
Short wavelength
High frequency
High energy
HOT

9. R O Y G B I V
The color you see is the wavelength that is reflected while all other color wavelengths are absorbed
EX: If you see green, that means green is reflected and all other colors are absorbed – plants have chlorophyll

10. COLOR
When all the colors of the rainbow are combined, we do not see any particular color, we just see light without any color.
We call this combination of all the colors of light "white light".

11. COLOR
To see colors, white light shines on an object, and the object absorbs all of the wavelengths of light it wants.
The object then reflects all of the other wavelengths it can’t use.
Our eyes see the reflected wavelengths and converts them to color.

12. COLOR
If all of the wavelengths of visible light are absorbed by the object, we see BLACK.
Black is not a color, it is the absence of color.

13. Why are plants green?
Plants absorb energy from light and convert it to chemical energy in the form of sugar (food for the plant).
Chlorophyll is an important molecule that absorbs blue and red light, and reflects green light.

14. Chlorophyll
Chlorophyll a is the main pigment in plants. It absorbs light mainly in the red and blue regions of the spectrum.
Chlorophyll b, xanthophyll and carotene are 'accessory pigments'.
They absorb light from other regions of the spectrum and pass the energy onto chlorophyll a.

15. Sound Waves

16. Check This Out!

17. Mechanical Waves
Mechanical Waves – waves that need a medium to transport energy and travel through
EX: Sound, Water, Seismic

18. Acoustic Waves Acoustic Waves – also known as sound waves
Vacuum – No matter exists; empty space where mechanical waves cannot travel

19. Interacting Particles
In a sound wave, air particles interact with each other
In a slinky wave, coils interact with each other
In a stadium wave, the fans interact with each other

20. More dense = Faster speed
Speed of Sound
Medium
Speed
Solid
Fast
Liquid
Gas (Air)
Slow
Vacuum
None
More dense = Faster speed

21. Speed of Sound As air temperature ↑, the speed of sound ↑

22. Pitch
Pitch – how high or low a sound seems to be –generated by the frequency of the wave

23. Amplitude
Amplitude – loudness of the sound (volume control)

24. How Sound is Created
Sound (human voice) is created by the vibrations in the vocal cords
Human Audio Frequency

25. Doppler Effect
Doppler Effect – the change in frequency and wavelength due to the motion of the source

26. Doppler Effect
Imagine a bug jiggling its legs and bobbing up and down in the middle of a quiet puddle
If the bug bobs in the water at a constant frequency, the wavelength will be the same for all successive waves
The wave frequency is the same as the bug’s bobbing frequency

27. Doppler Effect
Each wave crest has a shorter distance to travel so they arrive more frequently
The bug maintains the same bobbing frequency as before
However, an observer at B would encounter a higher frequency if the bug is moving toward the observer
Each crest has to travel farther than the one ahead of it due to the bug’s motion

28. Doppler Effect

29. Faster because it’s a liquid compared to a gas
Question
Is the speed of sound faster or slower in water compared to its speed in air?
Faster because it’s a liquid compared to a gas