The Study of Light

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Transcript The Study of Light

Video Field Trip: Fireball
How did scientists discover the
activity of the sun’s core?
How do auroras occur?
The Study of Light
Chapter 24, Section 1
Electromagnetic Radiation
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
Light has a dual nature, it is both a wave and a
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
Spectrum of Light
Concept Development
What are photons?
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
Compare and contrast the three
different types of spectra.
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
The Doppler Effect
Measurement of Doppler Shifts
Concept Check
How can scientists determine whether
a star is moving toward or away from
Read Chapter 24, Section 1 (pg. 674-677)
Do Chapter 24 Assessment #1-34 (pg. 695696)