Chapter 2: Messages in Starlight

Vocabulary flashcards covering the nature of light, light measurement, atomic energy states, spectral types, the Doppler effect, and blackbody radiation based on lecture notes.

Light

Energy emitted by the Sun that your eyes can see, your skin can feel, and that damages your DNA.

Newton

Scientist associated with the idea that light is composed of particles.

Double Slits Experiment

Experiment conducted by Young that showed interference and diffraction, proving that light is a wave.

Maxwell

Scientist who showed that light is an electromagnetic wave.

Photoelectric Effect

The emission of electrons when light shines on a material.

Albert Einstein

Scientist who explained the photoelectric effect and established that light behaves as both a wave and a particle.

Wave-Particle Duality

The concluding theory stating that light has characteristics of both a wave and a particle.

Wavelength

The distance between two crests, measured in Nanometers or Angstroms.

Frequency

The number of waves per second, measured in Hertz.

Speed of Light (Roemer, 1675)

Measured in 1675 by Roemer based on the observation that it takes light time to travel the extra distance.

Ground State

The lowest energy state of an atom.

Excited State

A state in which an atom possesses more energy than its ground state.

Continuous Spectrum

A spectrum containing all wavelengths/colors over a continuous range, produced by a hot dense object.

Emission Spectrum

A spectrum showing bright lines at specific wavelengths, produced when an excited atom's electrons drop to lower energy levels and emit photons.

Absorption Spectrum

A spectrum featuring dark lines at specific wavelengths.

Spectral Lines

Lines caused by electrons changing energy levels, used to determine chemical composition, temperature, and motion.

Doppler Effect

The change in observed light caused by the motion of the source relative to the observer, providing information about the motion of stars and other astronomical objects.

Radial Velocity

The speed of motion of a source relative to the observer, allowing astronomers to tell if objects are moving towards us or moving away.

Blackbody Radiation

Electromagnetic radiation emitted by an object based on its temperature across a continuous range of frequencies/wavelengths.

Wien's Law

The principle that as the temperature of an object increases, the peak wavelength of emitted radiation decreases and heating objects causes them to become brighter.