lecture 6, september 9, 2010

ASTR 101-3, FALL 2010 1

LECTURE 6, SEPTEMBER 9, 2010

ASTR 101, SECTION 3 INSTRUCTOR, JACK BRANDT

jcbrandt@unm.edu

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Question 6

The wavelengths of emission lines produced by an element

a) depend on its temperature. b) are identical to its absorption lines. c) depend on its density.d) are different than its absorption lines.e) depend on its intensity.

Question 6

The wavelengths of emission lines produced by an element

a) depend on its temperature. b) are identical to its absorption lines. c) depend on its density.d) are different than its absorption lines.e) depend on its intensity.

Elements absorb or emit the same wavelengths of light based on their electron energy levels.

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PHOTON-1 (See Page 59)

• Photons are packets of electromagnetic radiation (Einstein 1905)

• Each photon has a specific energy such that: (photon energy) is proportional to the (frequency)

• A red-light photon has a frequency of 4 x 1014 Hz (or a wavelength of 750 nm)

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PHOTON-2 (See Page 59)

• A blue-light photon has a frequency of 7 x 1014 Hz (or a wavelength of 430 nm)

• So, the red photon has 4/7 the energy of the blue photon

• The energy of photons in the electromagnetic spectrum increases with increasing frequency and decreases with increasing wavelength

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PHOTON-3 (See Page 60)

• REMEMBER: LIGHT IS LIGHT !

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ASTROMONICAL SPECTROSC0PY-1

• COMPOSITION• ABUNDANCES• TEMPERATURE (WIEN’S LAW, BLACKBODY, OR

OTHER• PRESSURE (BROADENS LINES)

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ASTRONOMICAL SPECTROSCOPY-2

• ROTATION (DOPPLER EFFECT)• MAGNETIC FIELD (ZEEMAN EFFECT)• ELECTRIC FIELD (STARK EFFECT)• DOPPLER EFFECT, MOTION TOWARD OR AWAY

FROM THE OBSERVER

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a) its spectral lines are redshifted.b) the light is much brighter.c) its spectral lines are shorter in wavelength.d) the amplitude of its waves has increased.e) its photons have increased in speed.

If a light source is approaching you, you will observe

Question 5

a) its spectral lines are redshifted.b) the light is much brighter.c) its spectral lines are shorter in wavelength.d) the amplitude of its waves has increased.e) its photons have increased in speed.

If a light source is approaching you, you will observe

Question 5

The Doppler Shift explains that wavelengths from sources approaching us are blueshifted.

Question 7

Analyzing a star’s spectral lines can tell us about all of these EXCEPT

a) its composition.b) its surface temperature.c) its transverse (side-to-side)

motion.d) its rotation.e) its density.

Question 7

Analyzing a star’s spectral lines can tell us about all of these EXCEPT

a) its composition.b) its surface temperature.c) its transverse (side-to-side)

motion.d) its rotation.e) its density.

Only motion toward or away from us influences

a star’s spectral lines.

Spectra can also tell us about a star’s magnetic

field.