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# How we see electromagnetic waves

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on 27 May 2013

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#### Transcript of How we see electromagnetic waves

By: Ada Bielawski Why is the sky blue? How does an object react to electromagnetic waves? * The electromagnetic spectrum arranges electromagnetic waves by their frequency (the higher the frequency and the smaller the wavelength, the more energy a wave carries.) Light is the small range of electromagnetic waves the human eye can see. How color affects light absorption: Many things can happen when these waves hit an object:
a) light is absorbed by the object, and the energy of the wave is converted to heat
b)a visible light consisting of many frequencies is "incident" toward the surface-->objects selectively absorb light. The object reflects some waves while absorbing others Electrons of atoms have a "natural frequency" at which they will vibrate. When a light wave with the same natural frequency hits the electrons, they will begin to vibrate. The vibrational energy is turned into thermal energy and the light is absorbed by the object. Thus different materials absorb different waves of light. What happens when the natural frequencies do not match? Reflection and transmission of light:
* The electrons vibrate (these vibrations are smaller than the ones mentioned before) for short periods of time, and the energy is re-emitted as a light wave.
--> if object is transparent, the vibrations are passed onto atoms near by and re-emitted on the other side of the object: TRANSMISSION
-->If object is opaque, the vibrations are not passed on, but the electrons on the material's surface vibrate and re-emit energy as a reflected light wave: REFLECTION The color of an object is the light that is reflected by the object and seen by our eyes. Only a small range of wavelengths can be seen by our eyes-- visible light-- which is between 400nm and 700nm on the electromagnetic spectrum. When light hits an object, it is either reflected/transmitted or absorbed. Visible light consists of ROYGBIV (red, orange, yellow, green, blue, indigo, and violet). When these waves hit an object, some our absorbed and some are reflected. The ones that are absorbed won't be seen, while the reflected ones will be seen.
-OYGBIV will be absorbed
- red will be reflected Reflects all colors Absorbs all colors Resources: http://www.physicsclassroom.com/Class/light/u12l2c.cfm Mrs. Collier's notes So white is really no color at all Sunlight reaches the atmosphere and is scattered by gases and air particles. This is called Rayleigh scattering. The longer waves pass through, while the shorter waves (blue) are absorbed by gas molecules and scattered in different directions. The sky fades to a lighter blue as you look closer to the horizon. This is because the sunlight has passed through more air, and has been scattered further. Sometimes the sky even looks white here. http://spaceplace.nasa.gov/blue-sky/ So then why does the sky look red during a sunset? The light passes through even more air as the sun gets lower. Consequently, more blue and green waves are scattered (shorter waves) and the longer wavelengths remain- the reds and yellows can be seen How does the color of electromagnetic waves affect the way we see things? Light travels in waves of vibrating electric and magnetic fields. Yellow is being reflected, and the remaining colors are being absorbed by the bananas. http://www.sciencemadesimple.com/sky_blue.html In order to understand this, we must know a bit about visible light (check!) and the atmosphere. The atmosphere is made up mostly of gas molecules (78% nitrogen and 21% oxygen) and tiny solid particles, like dust.
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