1 Matter and Radiation

Question 1

What is the structure of an atom?

Answer 1

• positively charged nucleus
• electrons surrounding the nucleus

Question 2

what are nucleons?

Answer 2

protons or neutrons in the nucleus

Question 3

what is an isotope?

Answer 3

atoms with the same number of protons but a different number of neutrons

Question 4

what is specific charge?

Answer 4

charge/mass

Question 5

why can an atom not have specific charge?

Answer 5

protons = electrons so charge = 0

Question 6

what does stable mean?

Answer 6

a substance does not disintegrate due to the strong nuclear force

Question 7

what are the properties of the strong nuclear force?

Answer 7

• range of 3 - 4 fm
• has the same effect between two protons, two neutrons or a proton and neutron
• attractive from 3 - 4 fm down to 0.5 fm
• repulsive below 0.5 fm to keep particles apart

Question 8

what are the properties of alpha decay?

Answer 8

• 2 protons and 2 neutrons (same as a helium nuclei)
• mass of 4
• charge of 2

Question 9

how is a beta minus decay produced?

Answer 9

a neutron splits into a proton and an electron

Question 10

what are the properties of beta decay?

Answer 10

• electron
• mass of 0
• charge of -1

Question 11

why is an antineutrino released in beta minus decay?

Answer 11

the energy of beta particles varied so there must be another particle

Question 12

what are the properties of gamma radiation?

Answer 12

• EM wave

Question 13

when is gamma radiation released?

Answer 13

when alpha and beta take place and there is extra energy

Question 14

what are the types of electromagnetic waves on the spectrum?

Answer 14

gamma
X-ray
UV
visible
Infrared
micro waves
radio waves

Question 15

what are the properties of waves near the gamma end?

Answer 15

short wavelength
high frequency

Question 16

what are the properties of waves near the radio waves end?

Answer 16

long wavelength
low frequency

Question 17

what are the properties of all EM waves?

Answer 17

they all travel at the speed of light in a vacuum

Question 18

what is the structure of EM waves?

Answer 18

• an electric wave and a magnetic wave
• at right angles to each other and the direction in which they travel
• in phase

Question 19

when are EM waves emitted?

Answer 19

when a charged particle loses energy:
- by being stopped
- by moving to a lower energy level (electrons)

Question 20

what is a photon?

Answer 20

when EM waves are emitted in short burst in any direction, each burst is a photon
(a packet of energy)

Question 21

what is the photoelectric effect?

Answer 21

when light is shone at a metal pate at the right frequency and an electron is emitted

Question 22

what is antimatter?

Answer 22

antiparticles that have the same rest mass and, if charged, have the equal and opposite charge to the corresponding particle

Question 23

what is a positron?

Answer 23

the antiparticle of the electron

Question 24

what happens in positron emission?

Answer 24

a proton turns into a neutron, positron and a neutrino

Question 25

where is positron emission used?

Answer 25

PET scanners

Question 26

what is Dirac’s theory?

Answer 26

for every type of particle there is an antiparticle that:
- annihilates the particle and itself when they meet and their mass is converted to two photons
- has exactly the same rest mass
- has exactly opposite charge

Question 27

what is pair production?

Answer 27

when a gamma photon changes into a particle and corresponding antiparticle

Question 28

what is one electron volt?

Answer 28

the energy transferred when one electron is moved through a p.d. of 1 volt

Question 29

what is a virtual photon?

Answer 29

the carrier of the electromagnetic force, a photon exchanged between two charged particles when they interact

Question 30

what is the weak nuclear force?

Answer 30

a force that causes decay. this must exist as the strong nuclear force does not account for decay

Question 31

what happens when a neutrino interacts with a neutron?

Answer 31

it causes the neutron to turn to a proton and a beta minus particle (electron)

Question 32

what happens when an antineutrino interacts with a proton?

Answer 32

it causes the proton to turn into a neutron and a beta plus particle (positron)

Question 33

what is a W boson?

Answer 33

the exchange particle of the weak nuclear force.

Question 34

what are the properties of W bosons?

Answer 34

• no rest mass
• short range of 0.001 fm
• W + or W - bosons exist

Question 35

what happens during beta decay if there is no neutrino or antineutrino?

Answer 35

• the W + boson decays into a beta minus particle and an antineutrino
• the W - boson decays into a beta plus particle and a neutrino

Question 36

what is electron capture?

Answer 36

when a proton turns into a neutron because of the weak interaction with an inner shell electron