Grade 12 Physics Revision: Quantum and Nuclear Physics

Comprehensive vocabulary flashcards covering basic quantum mechanics, atomic models, and nuclear physics revision notes.

Quantized Energy

The concept introduced by Planck stating that energy exists in specific discrete bundles or amounts rather than continuous waves.

Planck’s Constant ($h$)

A fundamental constant used in the equation $E = nhf$, with a value of approximately $6.63 \times 10^{-34} \, J \cdot s$.

Photoelectric Effect

The emission of electrons from a metal surface when it is exposed to electromagnetic radiation of a sufficient frequency.

Threshold Frequency ($f_0$)

The minimum frequency of incident light required to eject electrons from a specific metal surface.

Photocell

An evacuated tube containing a large electrode called a cathode and a smaller electrode called an anode used to study the photoelectric effect.

Photon

A discrete bundle or packet of light energy, according to Einstein's theory, where energy is defined as $E = hf$.

Electron Volt ($eV$)

A unit of energy equal to the energy gained by an electron moving across a potential difference of $1 \, V$, equivalent to $1.6 \times 10^{-19} \, J$.

Work Function ($\phi$)

The minimum energy needed to free an electron from a metal surface, equal to $hf_0$.

Stopping Potential ($\Delta V_0$)

The potential difference at which the electric field opposes electron motion so strongly that no photoelectrons reach the anode.

de Broglie Wavelength

The wavelength associated with a moving particle, calculated as $\lambda = \frac{h}{mv}$, describing the wave nature of matter.

Heisenberg Uncertainty Principle

A principle stating it is impossible to know both the precise position and precisely the momentum of a particle simultaneously.

Thomson's Atomic Model

An atomic model where electrons are distributed in a positively charged sphere, often compared to raisins in a muffin.

Rutherford’s Gold-Foil Experiment

An experiment using alpha particles that demonstrated atoms consist mostly of empty space with a dense, positively charged nucleus.

Emission Spectrum

A spectrum consisting of distinct bright lines emitted by a gas in a discharge tube, unique to each element.

Absorption Spectrum

A spectrum produced when white light passes through a gas, resulting in dark lines (Fraunhofer lines) at specific wavelengths.

Stationary State

A stable orbiting condition in Bohr’s model where an electron does not radiate energy.

Ground State

The lowest possible energy state of an atom; for hydrogen, this energy is approximately $-13.6 \, eV$.

Excited State

Any energy level of an atom that is higher than the ground state.

Schrödinger's Quantum Model

A model of the atom based on waves where the wave describes the probability of finding an electron in a region called an electron cloud.

LASER

An acronym for Light Amplification by Stimulated Emission of Radiation, producing coherent and monochromatic light.

Stimulated Emission

The process occurring when an excited atom is struck by a photon of the correct energy, causing the emission of an identical photon in phase.

Nucleons

The particles found in the nucleus of an atom, specifically protons and neutrons.

Isotopes

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Strong Nuclear Force

The powerful attractive force that acts between nucleons over very short distances, approximately $1.4 \times 10^{-15} \, m$.

Mass Defect ($\Delta m$)

The difference between the sum of the individual nucleon masses and the actual mass of the nucleus.

Binding Energy

The energy required to separate a nucleus into its individual nucleons, calculated using $E = \Delta m c^2$.

Alpha Decay

Radioactive decay where a nucleus emits a helium-4 nucleus, decreasing the mass number by 4 and the atomic number by 2.

Beta-minus Decay

Radioactive decay where a neutron converts into a proton, emitting an electron (beta particle) and increasing the atomic number by 1.

Gamma Decay

The emission of high-energy photons from a nucleus which changes the energy state but not the mass or atomic number.

Transmutation

The process of one element changing into another element through radioactive decay.

Half-Life ($T_{1/2}$)

The amount of time required for half of the radioactive atoms in a sample to undergo decay.

Nuclear Fission

The splitting of a heavy nucleus into smaller pieces, triggered by the absorption of a neutron and releasing energy.

Nuclear Fusion

The combining of light nuclei to form a heavier nucleus, a process that powers the Sun and requires extremely high temperatures.

Moderator

A material in a nuclear reactor used to slow down neutrons to make fission more effective.