LECTURE 6, SEPTEMBER 9, 2010 ASTR 101, SECTION 3 INSTRUCTOR, JACK BRANDT 1ASTR 101-3, FALL 2010

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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.

ASTR 101-3, FALL

ASTR 101-3, FALL

ASTR 101-3, FALL 2010 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 Hz (or a wavelength of 750 nm)

ASTR 101-3, FALL 2010 PHOTON-2 (See Page 59) A blue-light photon has a frequency of 7 x 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

ASTR 101-3, FALL 2010 PHOTON-3 (See Page 60) REMEMBER: LIGHT IS LIGHT !

ASTR 101-3, FALL

ASTR 101-3, FALL

ASTR 101-3, FALL

ASTR 101-3, FALL 2010 ASTROMONICAL SPECTROSC0PY-1 COMPOSITION ABUNDANCES TEMPERATURE (WIEN’S LAW, BLACKBODY, OR OTHER PRESSURE (BROADENS LINES)

ASTR 101-3, FALL 2010 ASTRONOMICAL SPECTROSCOPY-2 ROTATION (DOPPLER EFFECT) MAGNETIC FIELD (ZEEMAN EFFECT) ELECTRIC FIELD (STARK EFFECT) DOPPLER EFFECT, MOTION TOWARD OR AWAY FROM THE OBSERVER

ASTR 101-3, FALL

ASTR 101-3, FALL

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.