Transcript The Study of Light

Video Field Trip: Fireball
1.
How did scientists discover the
activity of the sun’s core?
2.
How do auroras occur?
The Study of Light
Chapter 24, Section 1
Electromagnetic Radiation
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Electromagnetic radiation includes gamma rays, Xrays, 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
Spectrum
Spectrum of Light
Concept Development
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What are photons?
Spectroscopy
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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
Three Types of Spectra
Solar Spectrum
Concept Check
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Compare and contrast the three
different types of spectra.
The Doppler Effect
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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
The Doppler Effect
Measurement of Doppler Shifts
Concept Check
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How can scientists determine whether
a star is moving toward or away from
Earth?
Assignment
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Read Chapter 24, Section 1 (pg. 674-677)
Do Chapter 24 Assessment #1-34 (pg. 695696)