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Light is a WAVE 5.2.1 EM Spectrum & EM Waves. EM Waves Charged objects generate electric fields. –When they move, the field changes. Changing electric.

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Presentation on theme: "Light is a WAVE 5.2.1 EM Spectrum & EM Waves. EM Waves Charged objects generate electric fields. –When they move, the field changes. Changing electric."— Presentation transcript:

1 Light is a WAVE 5.2.1 EM Spectrum & EM Waves

2 EM Waves Charged objects generate electric fields. –When they move, the field changes. Changing electric fields produce MAGNETIC FIELDS. Changing magnetic fields produce ELECTRIC FIELDS. The E-fields and B-fields are perpendicular to each other. Waving a charge back and forth generates an EM WAVE. Require a medium Do not require a medium

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4 The Speed of Light (well, EM Waves really) EM Waves travel at 3.0 x 10 8 m/s (in a vacuum). They are slower in denser mediums. Speed of a medium depends on INDEX OF REFRACTION. The closer the index is to 1.0 the faster the medium. Equation Index of RefractionSpeed of Light in vacuum Speed of Light in medium

5 What is the speed of light in a medium with an index of refraction of 2.0? n = c / v v = c / n v = (3 x 10 8 m/s) / (2.0) v= 1.5 x 10 8 m/s Example

6 EM Wave Types An EM Waves type depends on its frequency/wavelength 10 3 10 -2 10 -5 10 -7 10 -8 10 -10 10 -12 Wavelength (m) Freq (Hz) Temperature of bodies emitting the wavelength 1 K100 K10000 K10 million K 10 4 10 8 10 12 10 15 10 16 10 18 10 20 About the size of… Building Human Honey Bee PinpointProtozoanMolecules Atoms Atomic Nuclei RadioMicrowaveInfraredVisibleUltravioletX-rayGamma Ray All objects emit EM radiation

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8 Practice 1.The constellation of Orion is a highly recognizable arrangement of stars. There are two very distinct stars in this constellation, Betelgeuse which is a red star and Rigel which is a bluish star. The color red has a wavelength of about 750 nm and the color blue has a wavelength of about 400 nm. a.Which color has the higher frequency? b.Which star is hotter, Betelgeuse or Rigel? BLUE RIGEL

9 Practice 2.An EM wave is traveling through outer space with a frequency of 8.0 x 10 13 hertz. a.What is the wavelength of this wave? v = fλ λ= v / f λ = (3.0 x 10 8 m/s) / (8.0 x 10 13 Hz) λ = (3.8 x 10 -6 m) b.What type of wave is this? Infrared

10 Practice 3.Listed below are the properties of several EM Waves. State whether the property given is a wavelength or frequency, then state which type of EM Wave it is. a.500000 hertz_____________________________ b.5.0 x 10 -9 meter_____________________________ c.3.0 x 10 13 hertz_____________________________ d.4.5 x 10 14 hertz_____________________________ e.200 meters_____________________________ frequency wavelength frequency radio X ray / UV infrared (IR) visible light (red) radio

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