electromagnetic waves. electromagnetic waves – waves that do not need a medium to travel and...
TRANSCRIPT
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 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
EM SpectrumEM Spectrum – range of EM waves
from low to high frequency
EM Spectrum
EM SpectrumLongest wavelength
Lowest frequency
Shortest wavelength
Highest frequency
Visible LightVisible Light – The part of the EM
spectrum that humans can see; from 700 [nm] to 390 [nm]
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
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".
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.
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.