Modern Physics

Question 1

Thermionic emission

Answer 1

The release of electrons from the surface of a hot metal

Question 2

Cathode rays

Answer 2

Streams of high speed electrons moving from the cathode to the anode in an evacuated tube

Question 3

The electron volt

Answer 3

The energy gained or lost by an electron when it moves through a potential difference of 1V

Question 4

Photoelectric effect

Answer 4

The release of electrons from the surface of a metal when light of suitable frequency falls on it

Question 5

The threshold frequency

Answer 5

The minimum frequency needed for photoemission to occur for a given metal

Question 6

Photon

Answer 6

A packet of electromagnetic energy

Question 7

Work function

Answer 7

The minimum energy required by a photon to remove an electron from the surface of a metal

Question 8

X-rays

Answer 8

High frequency electromagnetic radiation which are produced when accelerated electrons strike a metal target

Question 9

An emission spectrum

Answer 9

Produced when light from a luminous source undergoes dispersion

Question 10

Atomic number (Z)

Answer 10

The number of protons in an elements nucleus

Question 11

The mass number (A)

Answer 11

The total number of protons and neutrons in the nucleus of an atom

Question 12

Isotopes

Answer 12

Atoms that have the same atomic number but different mass numbers due to a different number of neutrons in the nucleus

Question 13

Radioactivity

Answer 13

The decay of a nucleus with the spontaneous emission of radiation

Question 14

Alpha radiation

Answer 14

Helium nuclei ejected from the nucleus of radioactive atoms

Question 15

Beta radiation

Answer 15

High speed electrons ejected from the nuclei of radioactive atoms

Question 16

Gamma radiation

Answer 16

High frequency electromagnetic radiation emitted from the nuclei of radioactive atoms

Question 17

Ionisation

Answer 17

Occurs when atoms become charged by losing or gaining electrons

Question 18

Electron

Answer 18

The sub atomic particle that orbits the nucleus

Question 19

Activity

Answer 19

Number of nuclei decaying per second

Question 20

Becquerel

Answer 20

Unit of activity equal to 1 disintegration per second

Question 21

Law of radioactive decay

Answer 21

The activity of a sample is directly proportional to the amount present

Question 22

Half life

Answer 22

The time taken for half the atoms present to decay

Question 23

Nuclear fission

Answer 23

The splitting up of a large nucleus into two smaller nuclei of roughly the same mass with the release of energy

Question 24

Nuclear fusion

Answer 24

The joining up of two smaller nuclei to form a larger nucleus with the release of energy