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Astronomy 1010 Planetary Astronomy Fall_2014 Day-16

Astronomy 1010 Planetary Astronomy Fall_2014 Day-16. Course Announcements. Smartworks Chapter 3: Wed. 10/01 Smartworks Chapter 4: Mon. 10/06 SW Ch. 5: Fri. 10/17 (subject to change) SW Ch. 6: Fri. 10/24 (subject to change ) Exam-2: Friday, Oct. 10 Read chapters 4, 5

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Astronomy 1010 Planetary Astronomy Fall_2014 Day-16

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  1. Astronomy 1010 Planetary Astronomy Fall_2014 Day-16

  2. Course Announcements • SmartworksChapter 3: Wed. 10/01 • Smartworks Chapter 4: Mon. 10/06 • SW Ch. 5: Fri. 10/17 (subject to change) • SW Ch. 6: Fri. 10/24 (subject to change) • Exam-2: Friday, Oct. 10 • Read chapters 4, 5 1st Quarter night – TONIGHT – 7:30pm in the Archwood parking lot or SSB atrium depending on weather.

  3. Almost all knowledge of the universe beyond Earth comes from light. • Light can tell us about objects in space: temperature, composition, speeds, and more.

  4. Light moves at 300,000 km/s in a vacuum. • First measured by Rømer when observing Jupiter’s moons. • Speed is slower in other materials, e.g., glass.

  5. Light is a wave of combined electricity and magnetism, called an electromagneticwave. • Changing electric and magnetic fields create a self-sustaining electromagnetic wave.

  6. Wavelength (): length between crests. • Amplitude: height. • Frequency (f): number of waves that pass by each second. • Period (P): time to complete one cycle.

  7. A long wavelength means low frequency. • A short wavelength means high frequency. • The speed of light, c,is constant.

  8. Visible spectrum: small range of wavelengths that humans can see. • Red light = longest wavelength ( ~ 750 nm). • Violet light = shortest wavelength ( ~ 380 nm). • “Roy G. Biv.”

  9. Visible light is just one small part of the electromagnetic spectrum: Gamma rays X-rays UV Visible IR Microwave Radio  increasing f decreasing

  10. Lecture Tutorial EM Spectrum: (pg. 47) • Work with a partner! • Read the instructions and questions carefully. • Discuss the concepts and your answers with one another. Take time to understand it now!!!! • Come to a consensus answer you both agree on. • If you get stuck or are not sure of your answer, ask another group.

  11. Concept Quiz—AM and FM On the FM dial, the frequencies run from 88 to 107 MHz (million cycles per second). On the AM dial, the range is 570 to 1600 kHz (thousand cycles per second). Which statements are true? • FM photons have shorter wavelengths than AM. • FM photons have higher energies than AM. • FM photons travel at the same speed as AM. • All the above statements are true.

  12. Photons • Light also behaves as a particle. • Photon: particle of light. • Photons carry energy and can have different amounts of energy. • Photons with high energy = light with high frequency. • Photons with low energy = light with low frequency. • Atoms can absorb or emit photons.

  13. Atoms have a dense nucleus of protons and neutrons. • Electrons surround the nucleus in a “cloud.”

  14. Electrons can have certain energies; other energies are not allowed. • Each type of atom has a unique set of energies. • Energy level diagram represents this. • Lowest energy is the ground state.

  15. Emission: An electron emits a photon and drops to a lower energy state, losing energy. • The photon’s energy is equal to the energy difference between the two levels.

  16. Absorption: An electron absorbs the energy of a photon, moving the electron to a higher energy level. • The photon’s energy has to be equal to the energy difference between the two levels.

  17. The spectrum of a cloud of glowing gas contains emission lines. • When viewed through a cloud of gas, a continuous spectrum will have absorption lines.

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