The Sun and Spectrum

Astronomers make their living by based on their knowledge of the electromagnetic spectrum. This unit focuses on the fundamental physical properties of light and general EM radiation, including aspects such as frequency, wavelength, and energy. In addition, since any object above absolute zero temperature must radiate energy, understanding the how to use Wien's Law and the Stefan-Boltzman law are crucial.

The standards related to the EM spectrum are listed below. Note that we will revisit these standards in later units, so you aren't expected to know everything listed under the Evidence column (yet). For example, you need to understand how to use Wien's Law, but not how to use it to determine if you're looking at a White Dwarf or a Neutron Star.

Standard	Chapter	EM Spectrum and Thermo	Evidence/Student can...
2.1	5	EM Radiation can be modeled using both waves and particles	Compute wavelength and frequency of a photon, compute the energy/momentum of a photon
2.2	5	different frequencies and wavelengths of EMR correspond to different energy regimes	Compute energy of a photon; Apply Wien's law to determine λ_max for a given temperature; use Wien's Law to determine nature of objects (WD vs. NS vs. BH)
2.3	5	The EM Spectrum encodes considerable information about the emitting object	Discuss how properties of matter are encoded in the spectrum; classify a main-sequence star and determine its major properties given spectral data; identify simple elements from spectral lines; determine object velocity by observing doppler shift of spectral lines, explain cause of emission vs. absorption lines
2.4	5	The observed wavelength/frequency of EM radiation is influenced by the motion of the emitting object	Determine relative motion of an object based on doppler shift; compute an object's radial velocity using Doppler shift; compute mass ratios in a binary star system
2.5	5	Hotter objects emit higher energy photons than cooler objects	Apply Wien's Law and the Stefan-Boltzman law to determine energy flux and photon flux; compute luminosity ratios;
2.6	5	brighter objects emit more photons than dimmer objects	Apply Stefan-Boltzman law to determine flux and distance of luminous object, determine luminosity ratios, explain the magnitude scale