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Lecture 11

Astronomy Lecture 11.docx

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Patrick Mc Graw

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Astronomy Lecture 11
Which photons excite electrons
- Light has energy
- Photons of the wrong wavelength are transmitted
- Excitation by collision is also possible
- The extra energy is released as new photons after a short while, and electron falls back to a
lower level
Chemical Fingerprints
- Each ion, atom, isotopes- have its own orbits/wavelengths
- We can use this as a finger print to look at each gas
- When we look at a spectrum we spread the white light up and we see characteristic lines
- We can also measure the Doppler shift of individual lines
Summarizing Kirchoff’s Laws
- Hot dense object produces a continuous spectrum
- Light at all wavelengths
- Low density gas produces an emission line spectrum
- Bright lights at specific wavelengths
Midterm: Helpful Information
- 50 multiple choice spanning
- Lecture notes from weeks 1-5
- Questions- Dates, exact numbers, equations
- Need to know relative sizes and distances
- How numbers are used to describe the Cosmos
- Examples of concepts and how to apply them, definitions, evidence for different ideas,
relationships between quantities, etc.
- Study tips- study actively
- Answer the review questions in your textbook
- On the review cards in the back of the textbook
- Review the online quizzes to date
- Try the links in the slides to the web-simulations
- More practice quizzes, videos, simulations on CourseMate
Lunar Phases
- Different parts of the side of the Moon that faces us become illuminates as it revolves around
the Earth- it looks different every day
- Waxing = Increasing
- Waning= Decreasing
Practice midterm question
- When does the first quarter Moon rise?
- At sunrise
- At about noon (right answer)
- At sunset
- At about midnight