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Physics > Unit 1: Matter and radiation > Flashcards

Unit 1: Matter and radiation Flashcards

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0
Q

What is a nucleon?

A

A proton or neutron in the nucleus.

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1
Q

What do we know from Rutherford’s alpha-scattering experiment?

A

Every atom contains a positively charged nucleus made up of protons and neutrons that makes up most of the mass of the atom and there are electrons that surround the nucleus.

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2
Q

Why are electrons held in the atom?

A

They are negatively charged and the nucleus is positively charged so due to the electrostatic force, there is a force of attraction that holds the atom together.

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3
Q

Does the electron have a much smaller mass than the proton and neutron?

A

Yes

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4
Q

Do the proton and neutron have an almost equal mass?

A

Yes

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5
Q

What is the charge on the proton, neutron and electron?

A

A proton has a positive charge which is the same magnitude as the charge of an electron which is negatively charged and the neutron is neutral.

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6
Q

What is another name for the proton number?

A

The atomic number.

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7
Q

What are isotopes?

A

Atoms of the same element with different numbers of neutrons.

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8
Q

What is another name for the nucleon number?

A

Mass number

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9
Q

How can you calculate the number of neutrons in an element?

A

Nucleon number - proton number

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10
Q

Each type of nucleus is called…

A

A nuclide

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11
Q

How do you work out specific charge?

A

Charge/mass

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12
Q

Which particle has the largest specific charge?

A

The electron

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13
Q

What is equal in an uncharged atom?

A

The amount of protons and electrons.

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14
Q

What is a charged atom?

A

An ion

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15
Q

How does an uncharged atom become an ion?

A

Through gaining or losing electrons.

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16
Q

What is the force holding a nucleus together?

A

The strong nuclear force

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17
Q

What is the range of the strong nuclear force?

A

About 3-4 femtometres.

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18
Q

What range does the electrostatic force have?

A

An infinite range.

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19
Q

What are alpha particles made up of?

A

Two protons and two neutrons

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20
Q

What happens in beta minus decay?

A

A neutron in the nucleus turns into a proton, a beta particle is emitted as well as an antineutrino.

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21
Q

When does beta minus decay occur?

A

When the nucleus has too many neutrons.

22
Q

What is gamma radiation?

A

Electromagnetic radiation emitted by an unstable nucleus.

23
Q

When is gamma emitted from a nucleus?

A

When a nucleus has too much energy after an alpha or beta emission.

24
Q

List the electromagnetic spectrum starting with the one that has the largest wavelength.

A

Radio, microwave, infrared, visible, ultraviolet, x-Ray, gamma rays.

25
Q

What does an electromagnetic wave consist of?

A

An electric wave and a magnetic wave.

26
Q

How do the waves in the electromagnetic wave travel together and vibrate?

A

They vibrate together at right angles to each other and to the direction which they are travelling and in phase with each other - they reach a peak together.

27
Q

When are electromagnetic waves emitted?

A

When a charged particle loses its energy e.g. a fast-moving electron is stopped or an electron in a shell of an atom moves to a different shell of lower energy.

28
Q

What is a photon?

A

A packet of electromagnetic waves.

29
Q

What are the units of planck’s constant?

A

Js

30
Q

How do you calculate power?

A

Nhf where n is the number of photons.

31
Q

What is a positron?

A

The antiparticle of an electron

32
Q

How do PET scanners work?

A

A positron emitting isotope is given to the patient and some of it reaches the brain through the blood system, each positron doesn’t travel every far before it meets an electron, they annihilate each other and two gamma photons are produced as a result which are sensed by detectors.

33
Q

What happens in beta plus decay?

A

A proton turns into a neutron, a positron is emitted with a neutrino.

34
Q

Why does beta plus decay occur?

A

When there are too many protons in the nucleus.

35
Q

What is rest mass?

A

The mass of a particle when it is stationary.

36
Q

What unlocks rest energy (energy locked up as mass)?

A

Annihilation

37
Q

What happens when a particle and antiparticle meet?

A

They annihilate each other and their total mass is converted into photons.

38
Q

What is the difference between a particle and antiparticle? What is the same?

A

They have opposite charges however the same mass.

39
Q

What happens in pair production?

A

A photon with enough energy could turn into a particle-antiparticle pair.

40
Q

What is one MeV equivalent to?

A

1.6 x 10^-13 J

41
Q

What is one electron volt?

A

The energy transferred when an electron is moved through a potential difference of 1V.

42
Q

Why are two photons produced in annihilation?

A

As a single photon would take away momentum which isn’t allowed - no outside force are acting.

43
Q

What is the minimum energy of each photon produced?

A

Hfmin = E0

44
Q

What is the minimum energy of photon needed?

A

Hfmin = 2E0

45
Q

What is momentum?

A

Mass x velocity

46
Q

What happens when two objects interact?

A

They exert equal and opposite forces on each other. Momentum is transferred between these two objects.

47
Q

What is responsible for the electromagnetic force between two charged particles?

A

Due to the exchange of virtual photons

48
Q

Why are they called virtual photons?

A

We can’t detect them directly.

49
Q

What is the weak nuclear force responsible for?

A

Quark change.

50
Q

What are the exchange particles for the weak nuclear force?

A

W bosons

51
Q

What are the characteristics of a W boson?

A

They have a non-zero rest mass, they have a very short range of no more than about 0.001fm and they can be positively charged or negatively charged.

52
Q

What is electron capture?

A

When a proton in a proton-rich nucleus turns into a neutron as it interacts with an inner shell electron.

Physics (18 decks)

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