Modern physics

Cathode rays

Are streams of high speed electrons

The photoelectric effect

is the emission of electrons form the surface of a metal when light radiation of a suitable frequency falls on it.

A photon

is a discrete amount/packet of electromagnetic radiation

Thermionic Emission

is the giving of of electrons from the surface of a hot metal

X-Rays

are electromagnetic radiation of a high frequency

Ionisation

when an atom loses or gains an electron

The electron-volt

is the energy lost or gained by an electron when moves through a potential difference of one volt.

The Atomic number (Z)

tells us the number of protons present in the atom.

The Mass number (A)

Tells us the number of protons + neutrons present in the atom.

Isotopes

atoms which have the atomic number but a different mass number

Radioactivity/Radioactive decay

is the breakup of unstable nuclei with the release of one or more types of radiation

Half-life

of a material is the time taken for half of the nuclei in the sample to decay.

The Law of Radioactive Decay

states that the m=number of disintegrations per second is proportional to the number of nuclei present.

Nuclear Fission

is the break-up of a large nucleus into two smaller nuclei with the release of energy (and neutrons).

Nuclear Fusion

is the combining of two small nuclei to form one large nucleus with the release of energy.