Video Field Trip: Video Field Trip: FireballFireball

1.1. How did scientists discover the How did scientists discover the activity of the sun’s core?activity of the sun’s core?

2.2. How do auroras occur?How do auroras occur?

The Study of LightThe Study of Light

Chapter 24, Section 1Chapter 24, Section 1

Electromagnetic RadiationElectromagnetic 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

Electromagnetic Electromagnetic SpectrumSpectrum

Spectrum of LightSpectrum of Light

Concept DevelopmentConcept Development

What are photons?What are photons?

SpectroscopySpectroscopy Spectroscopy –Spectroscopy – the study of the properties of the study of the properties of

light that depend on wavelengthlight that depend on wavelength Continuous Spectrum –Continuous Spectrum – an uninterrupted an uninterrupted

band of light emitted by an incandescent solid, band of light emitted by an incandescent solid, liquid, or gas under pressureliquid, or gas under pressure

Absorption Spectrum –Absorption Spectrum – a continuous a continuous spectrum produced when white light is passed spectrum produced when white light is passed through a cool gas under low pressure; the gas through a cool gas under low pressure; the gas absorbs selected wavelengths of light, and the absorbs selected wavelengths of light, and the spectrum looks like it has dark lines spectrum looks like it has dark lines superimposedsuperimposed

Emission Spectrum –Emission Spectrum – a series of bright lines of a series of bright lines of particular wavelengths produced by a hot gas particular wavelengths produced by a hot gas under low pressureunder low pressure

When the spectrum of a star is studied, the When the spectrum of a star is studied, the spectral lines act as “fingerprints”spectral lines act as “fingerprints”

These lines identify the elements present and These lines identify the elements present and thus the star’s chemical compositionthus the star’s chemical composition

Three Types of SpectraThree Types of Spectra

Solar SpectrumSolar Spectrum

Concept CheckConcept Check

Compare and contrast the three Compare and contrast the three different types of spectra.different types of spectra.

The Doppler EffectThe Doppler Effect Doppler Effect –Doppler Effect – the apparent change in the apparent change in

frequency of electromagnetic or sound waves frequency of electromagnetic or sound waves caused by the relative motions of the source caused by the relative motions of the source and the observerand the observer

The light from a source that is moving away The light from a source that is moving away from an observer appears redder than it from an observer appears redder than it actually is because its waves are lengthened actually is because its waves are lengthened (red-shift)(red-shift)

This effect is only visible to the human eye This effect is only visible to the human eye when objects are moving close to the speed of when objects are moving close to the speed of lightlight

In astronomy, the Doppler effect is used to In astronomy, the Doppler effect is used to determine whether a star or other body in determine whether a star or other body in space is moving away from or toward Earthspace is moving away from or toward Earth

Large Doppler shifts indicate higher speeds; Large Doppler shifts indicate higher speeds; smaller Doppler shifts indicate slower speedssmaller Doppler shifts indicate slower speeds

The Doppler EffectThe Doppler Effect

Measurement of Doppler Measurement of Doppler ShiftsShifts

Concept CheckConcept Check

How can scientists determine How can scientists determine whether a star is moving toward whether a star is moving toward or away from Earth?or away from Earth?

AssignmentAssignment

Read Chapter 24, Section 1 (pg. 674-Read Chapter 24, Section 1 (pg. 674-677)677)

Do Chapter 24 Assessment #1-34 (pg. Do Chapter 24 Assessment #1-34 (pg. 695-696)695-696)