Quantum

Question 1

Why is the strong force both attractive and repulsive?

Answer 1

To prevent the nucleus from collapsing or exploding

Question 2

When is the strong force attractive?

Answer 2

> 0.5 fm

Question 3

When is the strong force repulsive?

Answer 3

< 0.5 fm

Question 4

What is the force responsible for beta decay?

Answer 4

the weak force

Question 5

How strong is the weak force? (relative)

Answer 5

1 millionth of the strong force

Question 6

How does the range of the weak force compare to that of the strong force?

Answer 6

It has a smaller range

Question 7

What does the weak force act on?

Answer 7

Leptons and hadrons

Question 8

What are the types of beta decay?

Answer 8

β+ and β-

Question 9

When does beta decay occur?

Answer 9

When the nucleus emits an electron or a positron

Question 10

What does a free neutron decay into in beta decay?

Answer 10

A proton, an electron and an anti-neutrino

Question 11

What does a free proton decay into in beta plus decay?

Answer 11

A neutron, a positron and a neutrino

Question 12

What type of beta decay is it when a free neutron decays into a proton?

Answer 12

β-

Question 13

What type of beta decay is it when a free proton decays into a neutron?

Answer 13

β+

Question 14

Why it called β- decay when a neutron decays into a proton?

Answer 14

An electron is produced

Question 15

Why is it called β+ decay when a proton decays into a neutron?

Answer 15

A positron is produced

Question 16

What happens to the unaccounted-for energy in beta decay?

Answer 16

It is carried away by the neutrinos

Question 17

What happens if the nucleus is still unstable after emitting alpha or beta radiation?

Answer 17

It is in an excited state, and gives off gamma radiation

Question 18

What does the strong force overcome?

Answer 18

The electrostatic forces of repulsion between protons in the nucleus

Question 19

What type of particle are neutrinos?

Answer 19

Leptons

Question 20

When are electromagnetic waves emitted?

Answer 20

When a charged particle loses energy

Question 21

In what form is electromagnetic radiation emitted?

Answer 21

Photons - bursts or packets of energy

Question 22

How do photons travel?

Answer 22

In one direction only in a straight line

Question 23

What is one electron volt defined as?

Answer 23

The energy transferred when an electron is moved through a p.d. of 1V

Question 24

What will happen if a particle-antiparticle pair meet?

Answer 24

They will annhiliate each other, their mass is converted into two gamma ray photons

Question 25

What is pair production?

Answer 25

When a photon (γ) with enough energy can change into a particle antiparticle pair

Question 26

What particles does the strong interaction affect?

Answer 26

Hadrons

Question 27

Define ionisation energy

Answer 27

The energy required to remove an electron from an atom’s ground state

Question 28

Define excitation energy

Answer 28

The energy required to raise an electron from ground state to an excited state

Question 29

Define quantisation of energy levels

Answer 29

Energy levels take discrete/specific values of energy

Question 30

What are 2 ways to excite an atom?

Answer 30

Collision of free electron:
(colliding electron transfers KE to atom’s electrons -> atomic electron moves to higher shell)

Absorption of photon:
(incoming photon transfers E to atomic electron, BUT photon must have EXACT amount of energy to cause excitation)

Question 31

What happens when an excited electron de-excites?

Answer 31

A photon is emitted, equal to the change in E

Question 32

What is the difference between excitation and ionisation?

Answer 32

EXCITATION: electron goes up energy level, falls back down, photon is emitted

IONISATION: electron leaves atom, results in free electron + free atom

Question 33

The gold leaf electroscope is used to detect ______. When the stem and leaf become charged, the gold leaf is _________ by the stem and ________.
When the charge leaves the system so that the charge of the gold leaf and stem are _______, the gold leaf _____.

Answer 33

charge / repelled / rises / neutral / falls

Question 34

What happens in an atom when line spectra are produced?

Answer 34

When electrons in atoms are excited, a photon of a specific energy is emitted, which can be seen as different colours on the line spectra

Question 35

Why is the line spectrum of an element unique to that element and can be used to identify it?

Answer 35

Energy levels for each atom are unique, so photons produced for each atom are different.

Each element produces a unique set of spectral lines to identify them

Question 36

Why are there dark lines on the absorption spectrum?

Answer 36

-Dark lines correspond to the [photons missing from the continuous spectrum of PARTICULAR WAVELENGTHS

-these photons excite electrons in the gas because they have the EXACT energy equal to the energy levels in the atom

• E = hc/λ

Question 37

Why do interference patterns only occur sometimes?

Question 38

How to get absorption spectra

Answer 38

-shine lots of white light through cool gas
-only certain photons (colours) absorbed
-we see a black line where no night gets through

Question 39

How to get emission spectra

Answer 39

-shine light through a diffraction grating
-splits up the colours to show certain frequencies of light