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Light is a WAVE 5.2.1 EM Spectrum & EM Waves.

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Presentation on theme: "Light is a WAVE 5.2.1 EM Spectrum & EM Waves."— Presentation transcript:

1 Light is a WAVE 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


4 The Speed of Light (well, EM Waves really)
EM Waves travel at 3.0 x 108 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 Refraction Speed of Light in vacuum in medium

5 Example 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 108 m/s) / (2.0) v= 1.5 x 108 m/s

6 Temperature of bodies emitting the wavelength
EM Wave Types An EM Wave’s type depends on its frequency/wavelength 103 10-2 10-5 10-7 10-8 10-10 10-12 Wavelength (m) Freq (Hz) Temperature of bodies emitting the wavelength 1 K 100 K 10000 K 10 million K 104 108 1012 1015 1016 1018 1020 About the size of… Building Human Honey Bee Pinpoint Protozoan Molecules Atoms Atomic Nuclei Radio Microwave Infrared Visible Ultraviolet X-ray Gamma Ray All objects emit EM radiation


8 Practice 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. Which color has the higher frequency? Which star is hotter, Betelgeuse or Rigel? BLUE RIGEL

9 Practice An EM wave is traveling through outer space with a frequency of 8.0 x 1013 hertz. What is the wavelength of this wave? v = fλ λ= v / f λ = (3.0 x 108 m/s) / (8.0 x 1013 Hz) λ = (3.8 x 10-6 m) What type of wave is this? Infrared

10 Practice 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. hertz _______________ ______________ 5.0 x 10-9 meter _______________ ______________ 3.0 x 1013 hertz _______________ ______________ 4.5 x 1014 hertz _______________ ______________ 200 meters _______________ ______________ frequency radio wavelength X ray / UV frequency infrared (IR) frequency visible light (red) wavelength radio

11 End of 5.2.1

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