NCEA Level 3 Modern Physics Key Terms 2014

Mass deficit

The reduction in mass in a nuclear reaction (mass then converted to energy).

Mass number

Number of nucleons in a nucleus.

Nuclear reaction

A reaction that involves the rearranging of nucleons.

Nucleon

Protons or neutrons.

Paschen series

Infrared light produced by excited hydrogen electrons.

Photoelectric effect

Effect where metal surfaces releases electrons when struck by photons.

Photon

Packet of energy.

Plancks constant

h = 6.63 × 10⁻³⁴ Js

Constant relating energy and frequency.

Radiation

Emission of energy as particles (α, β) or waves (γ).

Rydbergs constant

R = 1.097 × 10⁷ m⁻¹

Relativistic

An effect which changes the value of a quantity e.g. mass at high velocities.

Spectra

Separation of the electromagnetic spectrum into its discrete frequencies (e.g. ROYGBIV for visible light).

Threshold frequency

The minimum frequency of photons that cause electrons to be emitted from a metal surface.

Wavelength

Distance between any two corresponding positions on a wave.

Work function

Minimum energy needed for electrons to escape a metal surface during a metal photoelectric effect.

Atomic line spectra

Spectral lines given out/absorbed by low pressure gases when they are excited.

Balmer series

Visible light produced by excited Hydrogen electrons.

Binding energy

Energy required to separate a nucleus into its nucleons.

Binding energy per nucleon

Energy required to separate a nucleus into its nucleons divided by the number of nucleons.

Continuous spectra

Separation of electromagnetic spectrum into its discrete frequencies (e.g. ROYGBIV for visible light) with no gaps (missing frequencies).

Electromagnetic spectrum

Family of waves (e.g. light) don't require medium, are transverse and travel at 3 × 10⁸ ms⁻¹ in a vacuum.

Electron-volt

Unit of energy gained by an electron when moved through 1 volt.

Energy absorption

The amount of energy taken in by an electron when excited.

Energy level

Fixed quantities of energy which an electron can have in an atom.

Fission

Nuclear reaction where one big nucleus splits into two smaller nuclei.

Frequency

The number of waves passing a point per second.

Fusion

Nuclear reaction joining two smaller nuclei to make one bigger nucleus.

Ground state

Lowest energy level an electron can have when orbiting an atom (n=1).

Incident

Moving towards (e.g. incident light strikes a mirror).

Ionise

When an electron is given enough energy to leave the atom.

Lyman series

Ultraviolet light produced by excited Hydrogen electrons.