# WAVES THE ELECTROMAGNETIC SPECTRUM. Waves are a method that enrgy uses to travel from one location to another Waves are the result of a vibration traveling.

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WAVES THE ELECTROMAGNETIC SPECTRUM

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

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

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

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

1 second.1s.3s.5s.7s.9s.2s.4s.6s.8s1s 10 Hz f = Period = 1/10 or 0.1

Wavelength (λ) in meters Frequency ( f ) in Hertz 10 -14 10 -12 10 -10 10 -8 10 4 10 -6 10 -4 10 -2 10 0 10 2 10 22 10 20 10 18 10 16 10 14 10 12 10 10 10 8 10 6 10 4 Gamma rays X rays UltravioletInfraredRadio Microwave TV, FM AM High Energy Low Energy R O Y G B I V

Electromagnetic Spectrum

Wave Uses

Relative Wavelength

What type of wave is it? Use EM spectrum  λ = 2.90 E-8 m  f = 6.35 E6 Hz  λ = 7.01 E-6 m  λ = 9.40 E-14 m  f = 1.52 E22 Hz  f = 3.99 E8 Hz  λ = 8.34 E-10 m  f = 2.76 E10 Hz

Calculating frequency, wavelength, period and velocity Symbol UnitEquation Wavelength λ (Lambda) Meters (m) λ = v/f Frequency f Hertz (Hz, s -1 ) f = v/λ f = 1/p Periodp s 1/f velocity of light v* Meters per second (m/s) v = f λ v = velocity *Speed of light ( 3.00 E8 ) c Meters per second (m/s) c = f λ

Speed of Light Speed of light (c) in a vacuum = 3.00 E8 meters per second (m/s) VacuumWater In any other medium you have to calculate velocity v=fλ v=fλ

1)The wavelength of an x-ray is 4.32 E-11 m. What is its frequency? 2)Ultraviolet radiation from the sun has a frequency of 2.49 E16 Hz. What is its wavelength? 3)An infrared ray has a frequency of 1.01 E10 Hz and a wavelength of 2.95 E-2 m. What is the speed of the wave? What is the wavelength? What is the frequency? What is the speed of the wave? f= c/λ 3.00 E8 m/s 4.32 E-11 m == λ =c/f 3.00 E8 m/s 2.49 E16 s -1 == 6.94 E18 Hz 1.20 E-8 m 1.01 E10 Hz x 2.95 E-2 m = 2.98 E8 m/s

Radio Stations Radio stations transmit their signal in megahertz (MHz) 1 megahertz = ? Hertz 10 6 98.5 MHz 1 MHz Hz x= 1 10 6 9.85 E7 Hz

Radio Station’s Wavelength What is the wavelength of these popular radio stations?  97.9 MHz (you have to convert to Hz first)  104.5 MHz  105.3 MHz 9.79 E7 Hz λ = c/f 3.06 m 1.045 E8 Hz λ = c/f 2.87 m 1.053 E8 Hz λ = c/f 2.85 m

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

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

Interference DestructiveDestructive ConstructiveConstructive + = + =

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

Color Wavelengths ColorROYGBIV λ (m) 7.00 E-7 6.50 E-7 6.00 E-7 5.50 E-7 4.70 E-7 4.30 E-7 4.00 E-7

Baaa aaaa! Lambda!

B D C 3 Hertz 2 Hertz A λ f

1 sec

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

0.25 m 0.50 m 0.75 m 1.00 m Period (time 1 swing) s Title 0 1.00 m No breaks! 0 3 String length (m)

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