WAVES THE ELECTROMAGNETIC SPECTRUM Waves are the result

WAVES THE ELECTROMAGNETIC SPECTRUM

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

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

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

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

Period = 1/10 or 0. 1 1 second . 1 s. 2 s. 3 s. 4 s. 5 s. 6 s. 7 s. 8 s. 9 s 1 s f = 10 Hz

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

Electromagnetic Spectrum

Wave Uses

Relative Wavelength

What type of wave is it? Use EM spectrum 1. λ = 2. 90 E-8 m 2. f = 6. 35 E 6 Hz 3. λ = 7. 01 E-6 m 4. λ = 9. 40 E-14 m 5. 6. 7. 8. f = 1. 52 E 22 Hz f = 3. 99 E 8 Hz λ = 8. 34 E-10 m f = 2. 76 E 10 Hz

Calculating frequency, wavelength, period and velocity Symbol Wavelength λ (Lambda) Unit Equation 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 *Speed of light (3. 00 E 8) v* Meters per second (m/s) c Meters per second (m/s) v=fλ v = velocity c=fλ

Speed of Light Speed of light (c) in a vacuum = E 8 3. 00 meters per second (m/s) In any other medium you have to calculate velocity Vacuum v=fλ Water

What is the wavelength? What is the frequency? What is the speed of the wave? 1) The wavelength of an x-ray is 4. 32 E-11 m. What is its frequency? 3. 00 E 8 m/s f = c/λ = = 6. 94 E 18 Hz 4. 32 E-11 m 2) Ultraviolet radiation from the sun has a frequency of 2. 49 E 16 Hz. What is its wavelength? 3. 00 E 8 m/s = 1. 20 E-8 m λ = c/f = 2. 49 E 16 s-1 3) An infrared ray has a frequency of 1. 01 E 10 Hz and a wavelength of 2. 95 E-2 m. What is the speed of the wave? 1. 01 E 10 Hz x 2. 95 E-2 m = 2. 98 E 8 m/s

Radio Stations • • Radio stations transmit their signal in megahertz (MHz) 1 megahertz = ? Hertz – 106 98. 5 MHz 1 x 106 Hz 1 MHz = 9. 85 E 7 Hz

Radio Station’s Wavelength What is the wavelength of these popular radio stations? 1) 2) 3) 97. 9 MHz (you have to convert to Hz first) λ = c/f 3. 06 m 1. 045 E 8 Hz λ = c/f 2. 87 m 105. 3 E 8 MHz 1. 053 Hz λ = c/f 2. 85 m 9. 79 E 7 Hz 104. 5 MHz

How fast is the speed of light? Going around the world 7. 5 times a second

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 Color λ (m) R O Y G B I V 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

Baaaaaaa ! Lambda!

B A C D 2 Hertz λ f 3 Hertz

1 sec

1 sec

1 sec

1 sec

Mas s 4 Mas s 3 Ma s s 2 Mas s 1 Period (time 1 swing) Title

String length (m) 1. 00 m 0. 75 m 0. 50 m 0. 25 m 0 Period (time 1 swing) s 3 Title No breaks! 0