Electromagnetic Waves

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

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

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

EM Spectrum

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

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

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

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

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".

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.

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.

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.

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.