Spectroscopy and Atomic Structure - Flashcards

Vocabulary flashcards covering key concepts from waves, spectroscopy, atomic structure, and related topics from the lecture notes.

Undisturbed state

The resting state of a medium before a wave passes; line is flat.

Amplitude

Maximum displacement of a point on a wave from its undisturbed position.

Direction of wave motion

The direction in which the wave energy propagates.

Intensity

Power per unit area carried by a wave; a measure of how much energy the wave delivers.

Frequency

Number of complete wave cycles that pass a point each second (measured in Hz).

Observer

The detector or person examining or measuring a wave.

True wavelength

The intrinsic wavelength in the source’s rest frame; observed wavelength may differ due to motion.

Source at rest

A light-emitting object that is stationary relative to the observer; its emitted wavelengths are unshifted.

Moving source

A source moving relative to the observer, causing a Doppler shift in observed wavelength.

Wave crests

The peaks of a wave; successive crests are spaced by the wavelength.

Wien’s Law

The peak wavelength of a blackbody spectrum shifts to shorter wavelengths as temperature increases (lambda_max ∝ 1/T).

Stefan’s Law

The hotter something is, the more energy (or heat) it gives off.

Spectroscopy

The study of how matter interacts with electromagnetic radiation, often by analyzing spectra.

Spectral lines

Bright or dark lines at specific wavelengths produced by transitions in atoms or molecules.

Spectroscope

An instrument that disperses light into a spectrum for analysis.

Continuous spectrum

A spectrum that contains all wavelengths; produced by hot, dense sources.

Emission lines

Specific wavelengths emitted by atoms when they transition from higher to lower energy levels.

Absorption spectrum

A continuous spectrum that shows dark lines where photons are absorbed.

Absorption lines

Dark lines in a spectrum where atoms absorb photons at particular wavelengths.

Hydrogen atom

The simplest atom with one electron; its spectral lines illustrate atomic transitions.

Photoelectric effect

Emission of electrons from a material when illuminated, providing evidence for photons.

Molecules

Two or more atoms bound together; have electronic, vibrational, and rotational energy levels.

Energy levels

Discrete allowed energies that electrons (and molecular motions) can occupy.

Photon

A quantum of electromagnetic radiation with energy E=hf.

Ground state

The lowest energy state of an atom or molecule.

Excited state

A higher energy state than the ground state; electrons move here when they gain energy.

Direct decay

An excited state decays directly to the ground state, emitting a single photon.

Cascade decay

An excited state decays stepwise through intermediate levels, emitting multiple photons.

Emission spectrum

A spectrum consisting of bright lines at characteristic wavelengths emitted by atoms.

Multielectron atoms

Atoms with more than one electron; produce more complex spectra than hydrogen.

Hydrogen Balmer series

Hydrogen emission lines from transitions to n=2 (e.g., Hα, Hβ, Hγ).

The electromagnetic spectrum

The range of all electromagnetic radiation, from gamma rays to radio waves.

Doppler shift

Change in observed wavelength due to relative motion between source and observer (redshift/ blueshift).

Redshift

Increase in observed wavelength, indicating the source is moving away.

Blueshift

Decrease in observed wavelength, indicating the source is moving toward the observer.

Atomic structure

Model of an atom with a nucleus (protons and neutrons) and electrons surrounding it.

Proton

Positively charged subatomic particle in the nucleus.

Electron

Negatively charged subatomic particle orbiting the nucleus.

Neutron

Electrically neutral subatomic particle in the nucleus.

Bohr model

Quantum model with quantized electron orbits explaining hydrogen’s spectral lines.

Energy shell

Discrete energy levels around the nucleus where electrons can reside.

Hydrogen emission wavelengths (434.2, 486.3, 656.5 nm)

Key hydrogen lines from transitions to n=2 (Balmer series): Hγ ~434 nm, Hβ ~486 nm, Hα ~656 nm.

Vibrational transitions

Energy changes in molecular vibrations, producing infrared lines.

Rotational transitions

Energy changes due to molecular rotation, producing microwave/radio lines.

Electronic transitions

Electron energy changes within molecules or atoms, often in visible/UV range.

Spectral fingerprint

A unique pattern of spectral lines that identifies a particular element or molecule.

Kirchhoff’s First Law

Hot, dense sources produce a continuous spectrum.

Kirchhoff’s Second Law

Hot, rarefied gas emits an emission spectrum.

Kirchhoff’s Third Law

Cool gas in front of a hot, dense source produces an absorption spectrum.

Sun absorption spectrum

A spectrum showing dark absorption lines produced by cooler gas in front of a hot continuum source, such as the Sun.

Spectral-line analysis

Using the wavelengths and intensities of spectral lines to determine composition and properties of a source.