Modern Physics

Question 1

Electron

Answer 1

A subatomic particle which orbits the nucleus full stop has a charge of e which is the fundamental quantity of charge

Question 2

Thermonic emissiom

Answer 2

The release of electrons from the surface of a hot metal

Question 3

Work function

Answer 3

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

Question 4

X Rays

Answer 4

Electromagnetic radiation of extremely high frequency, short wavelength which are produced when high speed electrons strike a heavy metal target

Question 5

Photoelectric effect

Answer 5

The release of electrons from the surface of a metal due to electromagnetic radiation of a suitable frequency hitting is

Question 6

Photon

Answer 6

A discrete packet of electromagnetic energy. Its energy depends on its frequency
E = hf

Question 7

Threshold frequency

Answer 7

The minimum frequency needed for photoelectric emission

Question 8

Protons

Answer 8

Positively charged nucleons with the same size charge as the electron

Question 9

Neutrons

Answer 9

Electrically neutral nucleons, they have slightly more mass than protons

Question 10

Atomic Number

Answer 10

The number of protons in the nucleus of an atom

Question 11

Mass number

Answer 11

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

Question 12

Isotopes

Answer 12

Ashams which have the same atomic number but different atomic mass

Question 13

Radioactivity

Answer 13

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

Question 14

Ionisation

Answer 14

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

Question 15

Penetration

Answer 15

The distance the radiation travels through a medium

Question 16

Radioisotope

Answer 16

An unstable isotope of an element that the case spontaneously, emitting radiation

Question 17

Alpha radiation

Answer 17

The emission of a helium nucleus from a large atom

Question 18

Beta radiation

Answer 18

The emission of an electron when a neutron decays into a proton

Question 19

Gamma radiation

Answer 19

The emission of high energy photons from an unstable nucleus

Question 20

Activity

Answer 20

The number of nuclei in a radioactive sample decaying per second

Question 21

1 Becquerel

Answer 21

Units of activity equaling 1 disintegration per second

Question 22

Law of radioactive decay

Answer 22

The activity of a sample is directly proportional to the amount of present
A=-λN

Question 23

Half life

Answer 23

The time taken for half of the atoms present in a radioactive sample to decay
T= ln2/λ

Question 24

Nuclear fission

Answer 24

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

Question 25

Nuclear fusion

Answer 25

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

Question 26

Chain reactions

Answer 26

Reactions were at least one neutron is released during each fission reaction

Question 27

1 electronvolt

Answer 27

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

Question 28

Critical mass

Answer 28

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

Question 29

Radiation

Answer 29

The emission of particles of matter or photons of energy

Question 30

Background radiation

Answer 30

Radiation that comes from environmental sources including the Earth’s crust, the atmosphere, cosmic rays and radioisotopes