1. Video Field Trip: Fireball
How did scientists discover the activity of the sun’s core?
How do auroras occur?

2. The Study of Light
Chapter 24, Section 1

3. Electromagnetic Radiation
Electromagnetic radiation includes gamma rays, X-rays, ultraviolet light, visible light, infrared radiation, microwaves, and radio waves
Electromagnetic Spectrum – the arrangement of electromagnetic radiation according to wavelength
All energy, regardless of wavelength, travels through the vacuum of space at the speed of light (300,000 km/s)
Light has a dual nature, it is both a wave and a particle
Each color of light has a specific wavelength (with red having the longest and violet having the shortest)
Photon – a small packet of light energy
Shorter wavelengths have more energetic photons

4. Electromagnetic Spectrum

5. Spectrum of Light

7. Concept Development
What are photons?

8. Spectroscopy
Spectroscopy – the study of the properties of light that depend on wavelength
Continuous Spectrum – an uninterrupted band of light emitted by an incandescent solid, liquid, or gas under pressure
Absorption Spectrum – a continuous spectrum produced when white light is passed through a cool gas under low pressure; the gas absorbs selected wavelengths of light, and the spectrum looks like it has dark lines superimposed
Emission Spectrum – a series of bright lines of particular wavelengths produced by a hot gas under low pressure
When the spectrum of a star is studied, the spectral lines act as “fingerprints”
These lines identify the elements present and thus the star’s chemical composition

9. Three Types of Spectra

10. Solar Spectrum

11. Concept Check
Compare and contrast the three different types of spectra.

12. The Doppler Effect
Doppler Effect – the apparent change in frequency of electromagnetic or sound waves caused by the relative motions of the source and the observer
The light from a source that is moving away from an observer appears redder than it actually is because its waves are lengthened (red-shift)
This effect is only visible to the human eye when objects are moving close to the speed of light
In astronomy, the Doppler effect is used to determine whether a star or other body in space is moving away from or toward Earth
Large Doppler shifts indicate higher speeds; smaller Doppler shifts indicate slower speeds

13. The Doppler Effect

14. Measurement of Doppler Shifts

15. Concept Check
How can scientists determine whether a star is moving toward or away from Earth?

16. Assignment Read Chapter 24, Section 1 (pg. 674-677)
Do Chapter 24 Assessment #1-34 (pg )