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, RADARMicrowaves – heating up foodInfrared waves – heat lamps, warmthVisible Light – what we can seeUltraviolet rays (UV) – causes cancer and vitamin DX-rays – too much exposure can cause cancerGamma rays – radiation, hulk, nuclear weapons
3 EM WavesALL 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 SpectrumEM Spectrum – range of EM waves from low to high frequency
6 Longest wavelength Lowest frequency EM SpectrumLongest wavelength Lowest frequencyShortest wavelengthHighest frequency
7 Visible LightVisible 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 VLong wavelength Low frequency Low energy COLDShort wavelengthHigh frequencyHigh energyHOT
9 R O Y G B I VThe color you see is the wavelength that is reflected while all other color wavelengths are absorbedEX: If you see green, that means green is reflected and all other colors are absorbed – plants have chlorophyll
10 COLORWhen 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 COLORTo 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 COLORIf 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.