Modern Physics

Question 1

Electron

Answer 1

An indivisible quantity of charge that orbits the nucleus of an atom.

Question 2

Thermionic Emission

Answer 2

The emission of electrons from the surface of a hot metal.

Question 3

Work Function

Answer 3

The minimum energy required to remove the loosest electrons from the surface of that metal.

Question 4

X-rays

Answer 4

Electromagnetic radiation of extremely high frequency

Question 5

Photoelectric Effect

Answer 5

The emission of electrons from the surface of a metal due to electromagnetic radiation of a suitable frequency hitting the metal.

Question 6

Photon

Answer 6

A bundle of light energy.

Question 7

Einstein’s Photoelectric Law

Answer 7

The energy of the fastest electron emitted is the difference between the energy of the photon and the work function of the metal.

Question 8

Threshold Frequency

Answer 8

The minimum frequency needed to cause photoelectric emission.

Question 9

Proton

Answer 9

Positively charged nucleons, with the same size of charge as the electron.

Question 10

Neutrons

Answer 10

Electrically neutral nucleons.

Question 11

Atomic Number

Answer 11

Number of protons in the nucelus of an atom.

Question 12

Mass Number

Answer 12

Number of protons and neutrons in an atom.

Question 13

Isotopes

Answer 13

Atoms with the same atomic number but different atomic masses.

Question 14

Radioactivity

Answer 14

The spontaneous emission of radiation due to the natural disintegration of an unstable nucleus.

Question 15

Radioation

Answer 15

The emission of particles of matter or photons of energy.

Question 16

Ionisation

Answer 16

The charging of a neutral atom or molecule when it loses or gains one or more electrons.

Question 17

Penetration

Answer 17

The distance the radiation travels through a medium.

Question 18

Radioisotopes

Answer 18

An unstable isotope of an element that decays (disintegrates) spontaneously, emitting radiation.

Question 19

Alpha emission

Answer 19

Emission of a helium nucleus from a large atom (4 2He)

Question 20

Beta emission

Answer 20

The emission of an electron when a neurtron decays into a proton. (e-)

Question 21

Gamma emission

Answer 21

The emission of high energy ohotons from an unstable nucleus.

Question 22

Activity

Answer 22

The rate of emissions from that source. (Bq)

Question 23

Half Life

Answer 23

Time taken for half the nuceli in a given sample to decay.

Question 24

Law of Radioactive Decay

Answer 24

The acivity of a radioactive source is proportional to the nu,ber of undecayed nuclei present.

Question 25

Fission

Answer 25

The splitting of a large nucleus into two smaller nuclei, of roughly equal mass, with emission of neutrons and release of energy.

Question 26

Chain Reactions

Answer 26

Reactions where at least one neutron is released during each fission reaction.

Question 27

Critical Mass

Answer 27

The minimum amount of fissile material needed in order for chain reactions to occur.

Question 28

Fusion

Answer 28

Combining of two small nuceli to form a larger nucleus, with the release of energy.

Question 29

Background radiation

Answer 29

Radiation coming from enviornmental sources such as Earth’s crust, the atmosphere and radioisotopes.