THE ELECTROMAGNETIC SPECTRUM WAVES THE ELECTROMAGNETIC SPECTRUM Essential Question: What are the wave variables and how do they relate to each other?

Electromagnetic Spectrum R O Y G B I V Wavelength (λ) in meters Visible light 10-14 10-12 10-10 10-8 10-6 10-4 10-2 100 102 104 Gamma rays Ultraviolet Infrared Radio Microwave X rays TV, FM AM 1022 1020 1018 1016 1014 1012 1010 108 106 104 Frequency (f) in Hertz High Energy Low Energy

Waves are the result of a vibration traveling from one location to another. Waves are a method that enrgy uses to travel from one location to another velocity Wave Energy input (vibration)

Types of Waves Longitudinal or compression – vibrate parallel to velocity. ex. Sound Transverse – vibrations perpendicular to velocity. ex. Light and water waves

Crest Amplitude .r λ f Wavelength (λ) in meters 1 Hertz Trough 2 Hertz Frequency (f) in Hertz (Waves per Second) Crest Amplitude Vertical displacement 1 Hertz .r 1 second Trough λ 2 Hertz f 3 Hertz

Period and Frequency of Vibrations period – time (seconds) it takes for 1 vibration (wave) to occur. frequency – number of vibrations (waves) in a second f = 1/p AND p = 1/f 10Hz has a period of 1/10th of a second Unit: s Unit: Hz or s-1

1 second Period = 1/10 or 0.1 .1s .2s .3s .4s .5s .6s .7s .8s .9s 1s f = 10 Hz

Electromagnetic Spectrum

Wave Uses

Relative Wavelength

What type of wave is it? Use EM spectrum λ = 2.90 x 10-8 m f = 6.35 x 10 Hz λ = 7.01 x 10-6 m λ = 9.40 x 10-14 m f = 1.52 x 1022 Hz f = 3.99 x 108 Hz λ = 8.34 x 10-10 m f = 2.76 x 1010 Hz

Calculating frequency, wavelength, period and velocity Symbol Unit Equation Wavelength λ (Lambda) Meters (m) λ = v/f Frequency f Hertz (Hz, s-1) f = v/λ f = 1/p Period p s 1/f velocity of light v* Meters per second (m/s) v = f λ v = velocity *Speed of light (3.00 x10 8) c c = f λ

Draw continuous Y axis 4 sq from left side all the way down Calculate amplitude sq. + 1. Count down from the top this many squares and draw your x axis all the way across Dots represent wavelength, dashes represent half a wavelength: calculate # of sq. for wavelength and make your dots (number of dots is determined by # of vibrations) In between each dot along your x axis make your dashes Calculate # of sq. for amplitude. Make a dot in between dashes and dots up the correct number of dots. Alternate this for crest and trough Connect the dots to form your wave.

In any other medium you have to calculate velocity Speed of Light Speed of light (c) in a vacuum = 3.00 x108 meters per second (m/s) In any other medium you have to calculate velocity v=fλ Vacuum Water

Going around the world 7.5 times a second How fast is the speed of light? Going around the world 7.5 times a second

What is the wavelength. What is the frequency What is the wavelength? What is the frequency? What is the speed of the wave? The wavelength of an x-ray is 4.32 x 10-11 m. What is its frequency? Ultraviolet radiation from the sun has a frequency of 2.49 x 1016 Hz. What is its wavelength? An infrared ray has a frequency of 1.01E10 Hz and a wavelength of 2.95 x 10-2 m. What is the speed of the wave? 3.00x108 m/s 4.32x10-11 m f = c/λ 6.94 x1018 Hz = = 3.00x108 m/s 2.49x1016 s-1 λ = c/f 1.20x10-8 m = = 2.98x108 m/s 1.01x1010 Hz x 2.95x10-2 m =

Radio Stations Radio stations transmit their signal in megahertz (MHz) 1 megahertz = ? Hertz 106 98.5 MHz 106 Hz 9.85x 107 Hz x = 1 1 MHz

Radio Station’s Wavelength What is the wavelength of these radio stations? 97.9 MHz (you have to convert to Hz first) 104.5 MHz 105.3 MHz 9.79 x 107 Hz λ = c/f 3.06 m λ = c/f 1.045 x108 Hz 2.87 m λ = c/f 1.053 x108 Hz 2.85 m

Interference Interference occurs when 2 waves occupy the same space at the same time. It can be “destructive” or “constructive”, depending if the waves are “in phase” or “out of phase”.

Interference Destructive Constructive + = + =

v=fλ In a vacuum v = (c) speed of light In any other medium you have to calculate velocity Faster =  f or ↓ λ Slower = ↓f or  λ

Color Wavelengths λ (m) R O Y G B I V Color 7.00E-7 6.50E-7 6.00E-7

Baaaaaaa! Lambda!

A B C D 2 Hertz λ f 3 Hertz

1 sec

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Title Period (time 1 swing) Mass 1 Mass 2 Mass 3 Mass 4

Title 3 Period (time 1 swing) s No breaks! 0.25 m 0.50 m 0.75 m 1.00 m 0.25 m 0.50 m 0.75 m 1.00 m 1.00 m String length (m)