Light, Spectra, and the Doppler Effect

Vocabulary flashcards covering atomic transitions, blackbody radiation laws, types of astronomical spectra, chemical fingerprints, and the Doppler effect.

Absorption

The process where an atom absorbs energy from a photon, causing an electron to move away from the nucleus and jump to higher energy levels.

Emission

The process where an atom emits energy in the form of a photon, causing an electron to transition down to energy levels closer to the nucleus.

Spectrum

The pattern formed when light coming from an object is spread out across its individual wavelengths, such as by passing through a prism.

Blackbody Spectrum

A characteristic curve plotting wavelength versus intensity that shows how much light an object radiates across different wavelengths.

Stefan-Boltzmann Law

The principle stating that a hotter object radiates more total energy, establishing a direct relationship where energy output (flux) is proportional to temperature to the fourth power ($T^4$).

Flux ($F$)

The rate of energy output describing how much energy comes out of an object over a given area over time.

Wien's Law

The inverse relationship stating that the peak wavelength of a blackbody spectrum shifts toward shorter wavelengths as the object's temperature increases.

Continuous Spectrum

An unbroken rainbow of all wavelengths and colors of light, produced when observing light emitted directly from a hot, dense source.

Absorption Spectrum

A spectrum showing dark absorption lines or dips of missing light, created when light from a hot, dense source passes through a cooler gas cloud or atmosphere.

Emission Spectrum

A spectrum consisting of distinct bright lines at specific wavelengths, produced when excited atoms in a hot, low-density gas emit photons.

Diffraction Grating

A material with tiny microscopic grooves that causes incoming light to spread out into spectra similar to a prism.

Chemical Fingerprint

The unique, characteristic pattern of spectral lines produced by a specific element or atom, used by astronomers to determine an object's chemical composition.

Radial Velocity

The speed of an astronomical object directed along the line of sight, moving either straight towards or away from the observer.

Doppler Effect

The perceived change in the wavelength or frequency of a wave caused by the relative motion between the emitting source and the observer.

Doppler Equation

The equation $\frac{\Delta\lambda}{\lambda_0} = \frac{v}{c}$, which directly relates the shift in wavelength relative to the rest wavelength to an object's radial velocity divided by the speed of light.

Blue Shift

The shift of spectral wavelengths toward shorter, smaller values, indicating that the light-emitting source is moving towards the observer.

Red Shift

The shift of spectral wavelengths toward longer, larger values, indicating that the light-emitting source is moving away from the observer.