Modern Physics Flashcards

Flashcards based on lecture notes for exam preparation covering topics in modern physics.

Quantum Theory

Electromagnetic energy is emitted from and absorbed by matter in discrete amounts or packets.

Energy of a Quantum

The amount of energy E of each quantum is directly proportional to the frequency f of the electromagnetic radiation.

Photon

A massless particle of light that carries both energy and momentum.

Photon Energy Equation

Ephoton = hf = hc/λ (energy of a photon is directly proportional to its frequency and inversely proportional to its wavelength)

Photon-Particle Collisions (X-ray)

When X-ray photons strike a metal surface, electrons are ejected, and electromagnetic radiation of lower frequency is given off.

Wave Nature of Particles

Matter in motion has wave as well as particle characteristics.

Atom

The smallest particle of an element that retains the characteristics of that element.

Thomson's Model of the Atom

The atom consists of a uniform distribution of positive charge in which electrons are embedded.

Rutherford's Model of the Atom

The massive, energetic, positively charged particles must have collided with other even more massive positively charged particles concentrated in the atom's center.

Bohr's First Assumption

All forms of energy are quantized; an electron can gain or lose kinetic energy only in fixed amounts, or quanta.

Bohr's Second Assumption

The electron in the hydrogen atom can occupy only certain specific orbits of fixed radius and no others.

Bohr's Third Assumption

The electron can jump from one orbit to a higher one by absorbing a quantum of energy in the form of a photon.

Bohr's Fourth Assumption

Each allowed orbit in the atom corresponds to a specific amount of energy.

Stationary State

When an electron is in any particular orbit

Ground State

The lowest energy level (n=1) for an electron in an atom.

Excited State

Any level above n=1 for an electron in an atom.

Excitation

Any process that raises the energy level of electrons in an atom.

Spectral Line

A particular frequency of absorbed or emitted energy characteristic of an atom.

Ionization Potential

The energy required to remove an electron from an atom to form an ion.

Cloud Model of the Atom

Electrons are spread out in space in a form called an electron cloud, densest where the probability of finding the electron is highest.

Atomic Spectrum

A specific series of frequencies of electromagnetic radiation produced when the electrons in excited atoms of an element in the gaseous state return to lower energy levels.

Bright-Line Spectrum (Emission Spectrum)

A series of bright lines against a dark background, characteristic of an element, produced when electrons of its atoms in excited states fall to lower energy levels.

Absorption Spectrum

A series of dark lines resulting from the selective absorption of particular frequencies in the white-light spectrum of an atom.

Ground state

The lowest energy state of an atom.

the relationship between possible energy in the hydrogen spectrum

The energy emissions producing various series of lines in the ultraviolet, visible light, and infrared regions.