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.