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nature of light By reading this chapter, you will learn

5-1 How we measure the speed of light 5-2 How we know that light is an electromagnetic wave 5-3 How an object’s temperature is related to the radiation it emits 5-4 The relationship between an object’s temperature and the amount of energy it emits

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nature of light By reading this chapter, you will learn

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  1. 5-1 How we measure the speed of light 5-2 How we know that light is an electromagnetic wave 5-3 How an object’s temperature is related to the radiation it emits 5-4 The relationship between an object’s temperature and the amount of energy it emits 5-5 The evidence that light has both particle and wave aspects 5-6 How astronomers can detect an object’s chemical composition by studying the light it emits 5-7 The quantum rules that govern the structure of an atom 5-8 The relationship between atomic structure and the light emitted by objects 5-9 How an object’s motion affects the light we receive from that object nature of lightBy reading this chapter, you will learn

  2. Olaus Rømer (1676) Fizeau and Foucalt (1850) d=rt again gave c Determining the Speed of Light Galileo

  3. Young’s Double-Slit Experiment – wave like properties (1801) I. Newton - particle-like properties C. Huygen – wave nature

  4. James Clerk Maxwell (1860s) wave nature: electromagnetism • Because of its electric and magnetic properties, light is also called electromagnetic radiation • Visible light falls in the 400 to 700 nm range • Stars, galaxies and other objects emit light in all wavelengths

  5. electromagnetic radiation around you

  6. Three Temperature ScalesSee box 5-1 (pg. 105) • Temperature conversion • Tf = 9/5 Tc +32 • Tc = 5/9 (Tf -32) • TK = Tc + 273

  7. How are you doing? • Who was the first person to come up with a method to measure a reasonable value of speed of light? • Huygen’s idea of light was light as _____, which was different from Newton’s view of light. A) particle, b) wave, c) part of electromagnetic radiation, d) photons of various energy level • Light part of electromagnetic radiation. What type of electromagnetic radiation is high energy? A) radio wave, b) visible light, c) Ultraviolet, d) infrared, e) gamma ray

  8. Put the following color in the order of cooler to hotter: Yellow, Red, Orange, Blue, white

  9. Black body radiation Wien’s law lmax ~ 1/Temp Stefan-Boltzmann law Luminosity ~ T4 Planck’s law E ~1/l This is the method we used to determine the surface temperature of the sun. @1AU, we receive 1370W /m2

  10. Each chemical element produces its own unique set of spectral lines

  11. Kirchhoff’s Laws

  12. Red Shift: The object is moving away from the observer • Blue Shift: The object is moving towards the observer Doppler effect

  13. Properties of light • Which color is hotter? A) blue, b) red, c) yellow, d) white • Which type of sprctra is produced by hot thin gas? A) continuous spectrum, b) absorption spectrum, c) emission spectrum • Longer wavelength means: a) higher energy, b) lower energy • Bohr model explains: • If a star is moving away from us, the star will suffer: a) blue shift, b) red shift, c) both blue and red shift. • If a star is rotating fast, the star will suffer: a) blue shift, b) red shift, c) both blue and red shift.

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