AST- 105 1st EditionLecture 5Outline of Last LectureI. Heat and RadiationII. Temperature ScalesIII. Black Body RadiationOutline of Current LectureI. SpectroscopyII. Kirchoff’s LawsCurrent LectureI. Spectroscopya. Spectrum- the array of wavelengths produced when light is dispersed by a prism or grating. i. Spectra provide information on physical conditions at light source. b. Spectral line- sharp dip or peak in a spectrum at a characteristic wavelength.c. Intensity- a measure of brightness at a particular wavelength.II. Kirchoff’s Lawsa. Kirchoff’s Law 1- a hot solid object or dense gas produces a continuous spectrum.i. Complete rainbowii. All wavelengths seeniii. No spectral linesiv. Examples:1. Incandescent lights2. Heated bar of iron3. Ideal Black Bodyb. Kirchoff’s Law 2- a low-density, hot gas produces an emission line spectrum.i. Series of bright lines ii. No emission between linesiii. Examples:1. Neon signs2. Chromospheres of the Sun3. Bright interstellar
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