Light and the Electromagnetic Spectrum

Electromagnetic Spectrum The electromagnetic spectrum is a scale showing how light can be classified. (aka, heat or radiation) All electromagnetic waves travel at the speed of light. The basic difference between each type of wave is it’s wavelength.

The Different types of Light Radio Microwaves Infrared Visible Ultraviolet X-rays Gamma rays Real Men In Violet Underwear (are) Xtremely Gorgeous

Use of the EM Spectrum How is the EM spectrum used or seen on a daily basis? What superheroes use the EM spectrum? How astronomers use the electromagnetic spectrum? –Looking at celestial objects in different waves allows us to see different aspects of that objects

Visible Light The only part of the spectrum that we can see is the visible area of the spectrum. That visible part is very small. If you laid out the EM Spectrum scale over 200 miles, the visible spectrum would only cover 2 in!

The EM Spectrum classifies radiation (light) by the length of the wave. Classification

Anatomy of a Wave  Wavelength- DISTANCE from crest to crest or trough to trough.  Defines the type of waver it is.

Frequency Frequency- TIME it takes the wave to pass a point from crest to crest. (or trough to trough) What happens to Frequency as wavelength gets bigger? XXXXXXxXXXXXXx

Inversely Proportional We say that wavelength and frequency are inversely proportional. This means that changes in frequency results in the OPPOSITE change of wavelength. As wavelength increases, frequency decreases. (less frequent)

Speed of Light  Regardless of frequency or wavelength, the wave always travels at 300,000 km/s (186,000 mi/s) also known as the speed of light.

Wavelength and frequency Speed of light- c C= 300,000 km/sec Frequency- f Wavelength- λ c=(f)λ

Using the EM Spectrum

A word about color  When you see black, all colors are being absorbed by something.  When you see white, all colors are being reflected off of something. Like this text  You see color when everything is being absorbed EXCEPT that color: This text is black. It is absorbing all colors from white light This text is red. Every color EXCEPT red is being absorbed.

Seeing inside the Light  White light isn’t really white (or clear) instead it has ALL the colors of the rainbow.  Spectroscopes are tools astronomers use that bend visible light using a prism.  This bend causes the white light to “break up” into its composite colors.

When “pure white” light bends through a prism, we see all the colors in the rainbow. When the light you are looking at is showing a all colors like this, you have a continuous spectrum

Spectral Lines  In Astronomy, there is a lot of dust and gas in space through which light must travel.  Going through a HOT gas allows us only able to detect colors that are emitted (NOT absorbed) forming an EMISSION SPECTRUM.  Light easily goes through a COLD so we can see all colors except those that are absorbed.  The lines are EXACTLY the reverse of emission lines.

Unique Fingerprints Each gas has its own unique spectra, like DNA no two elements emit the same wavelengths. We use spectral lines of an element to identify it in a star- like matching DNA to a culprit’s saliva... We usually use the emission spectra because there are less lines to compare.

Telescopes  Telescopes have been developed to read all areas of the spectrum. We can “see” a stars’ x-rays or radio waves.

Sun in UV Waves Sun in X-rays

Sun in radio waves Sun in Infrared waves

Potential Quiz Questions What are the major parts of the Electromagnetic Spectrum? How can you tell the difference between a continuous, absorption and emission spectrum?

How can we obtain most of our knowledge from the sun? the solar system?, the universe? What is a wave’s frequency? wavelength? Potential Quiz Questions