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gcse physics > P6 Radiation > Flashcards

P6 Radiation Flashcards

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1
Q

explain radio-isotopes

A

the balance of protons to neutrons is critical for the nucleus to hold itself together. If the balance is wrong, then a nucleus is unstable and will decay.

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2
Q

true/false - most naturally occurring isotopes are stable

A

true - most naturally occurring isotopes are stable

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3
Q

how can unstable isotopes become stable?

A

by releasing different types of particles

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4
Q

what is the term radiation referring to?

A

the particles/waves emitted by the nuclei of radioactive substances.

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5
Q

what are the elements that undergo radioactive decay called?

A

radioisotopes/radionucleids

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6
Q

what kind of process is radioactive decay

A

spontaneous + random

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7
Q

define/explain radioactive decay

A

the random disintegration of an unstable nucleus by the emission of particles or electromagnetic radiation. After radioactive decay has taken place, the resulting nucleus is more stable. It may now be a different element.

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8
Q

how would you write an aloha decay equation?

A

because alpha decay uses a helium nucleus, you minus four from the top number and two from the bottom number.

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9
Q

what is a beta particle?

A

a fast moving electron which is emitted from the nucleus of an atom undergoing radioactive decay.

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10
Q

how would you write a beta decay equation?

A

the atomic number (bottom) increases by 1 and the mass number stays the same

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11
Q

what are gamma particles?

A

gamma particles aren’t charged particles like alpha/beta. Gamma rays are electromagnetic radiation with high frequency.

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12
Q

explain ionisation

A

when a radioactive atom comes into contact with another atom, changing its number of electrons

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13
Q

which types of radiation are the most and least ionising?

A

alpha is the most ionizing (heaviest could knock out an electron)
and gamma is the least ionizing

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14
Q

what would happen if an atom of a living thing is ionised

A

if an atom of a living thing is ionized, it damages cells.

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15
Q

how would you tell apart the decays?

A

an alpha particle can’t penetrate paper
beta particle can pass paper but not aluminum foil
gamma particles can be blocked by a 10cm block of lead, could penetrate and change the whole structure of your cells.

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16
Q

what is one way of measuring radioactivity?

A

a GEIGER COUNTER is used to detect and measure the amount of radioactive activity emitted by a radioactive source

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17
Q

define half life

A

the half life of a radioactive element is the time that it takes for half the remaining unstable nuclei in a sample to decay

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18
Q

what does it mean if a nuclei decays at a faster rate?

A

it is more unstable

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19
Q

explain net decline

A

you can use the half-life to calculate the ratio of the final to the initial activity.

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20
Q

define photon

A

a photon is described as a packet of energy that is absorbed or emitted as electromagnetic radiation

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21
Q

how can energy move between levels in the atom?

A

to move between energy levels, energy must be absorbed (taken in) or emitted

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22
Q

what is the movement between energy levels known as?

A

a quantum leap. this is a very small difference.

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23
Q

what does absorption cause for electrons?

A

it causes electrons to be excited

24
Q

what happens if you add the right amount of energy to an atom?

A

if you add the right amount of energy to an atom, the electron will jump up energy levels.

25
Q

what does emission cause for atoms?

A

it causes atoms to be de-excited

26
Q

what happens if the electrons drop down energy levels?

A

if the electron drops down energy levels, the atom gives up the same amount of energy

27
Q

what happens if the electron gets enough energy to escape entirely?

A

it becomes an ion

28
Q

what happens when light is passed through hydrogen gas?

A

when light of all frequencies is passed through hydrogen gas, some frequencies are absorbed. An absorption spectrum is produced

29
Q

what does a prism do?

A

a prism disperses light into its constituent colours

30
Q

true/false - excited emissions always say excited

A

FALSE!! excited electrons don’t stay excited forever and eventually drop down to their ground floors.

31
Q

what happens when electrons move from a higher to lower level?

A

when electrons move from a higher to lower level, they emit radiation. An emission spectrum is produced.

32
Q

explain contamination

A

when radioactive particles get onto the objects - comes from touching and handling radioactive substances.

33
Q

what is contamination and irridation?

A

contamination is from an internal source/on skin with a LONG term exposure
irritation is form an external source usually with a SHORT term exposure

34
Q

what are the safety precautions for risk of contamination?

A

wear a radiation suit and wash after exposure

35
Q

what are the safety precautions for risk of irridation?

A

maintain distance and only be exposed to a small dose

36
Q

explain irridation

A

when objects are exposed to radioactive particles

37
Q

give two examples of uses for radioactivity in medicine

A

gamma camera and medical tracer

38
Q

what does a medical tracer do?

A

(beta/gamma emitter) used to investigate a patients body without the need for invasive surgery

39
Q

what does a gamma camera do?

A

makes an image of your organs to help diagnose disease

40
Q

why does the half life have to be very exact for a medical tracer?

A

if it is too short, the tracer can decay before the gamma camera is used. if it’s too long the tracer will emit radiation for a long time, increasing risk of cancer

41
Q

what else can gamma rays be used for?

A

gamma rays can be used to treat cancer. The radiation can damage the cancer cells to restrict their growth or kill them

42
Q

define nuclear fission

A

nuclear fission is when a NEUTRON splits a LARGE UNSTABLE NUCLEUS into two. This RELEASES ENERGY. THREE DAUGHTER neutrons are released to go and split other unstable nuclei. This is called a CHAIN REACTION

43
Q

what are the most commonly used isotopes in nuclear fission?

A

Uranium -235 and Plutonium -239

44
Q

explain critical mass

A

to keep a chain reaction going, there must be enough uranium to prevent too many neutrons escaping from the sides. The mass of uranium needed to keep the reaction going is called the critical mass.

45
Q

what would happen if the fast neutrons produced in the reaction could be slowed down?

A

they could be used to induce further fission in other u-235 atoms

46
Q

summarize the steps of nuclear fission

A

1) a fast-moving neutron is absorbed by an atom of Uranium -235
2) the uranium -235 becomes uranium-236, an unstable atom
3) the uranium splits into 2 daughter nuclei and three neutrons
4) each of these uranium atoms undergoes fission, releasing even more neutrons
5) this is known as nuclear fission
6) each of the three neutrons can be absorbed by another atom of uranium -235
7) this is known as chain reaction

47
Q

how does a nuclear reactor produce?

A

a nuclear reactor uses a controlled chain reaction to produce heat to produce steam for a generator.

48
Q

explain an uncontrolled chain reaction

A

if the mass of uranium is too large, the rate of the fission reaction increases very rapidly, the temperature rises by thousands of degrees in a fraction of a second and a NUCLEAR EXPLOSION results.

49
Q

explain a controlled chain reaction

A

if the mass of uranium is a little lower and a material is used to ABSORB EXCESS NEUTRONS then the rate of fission can be controlled

50
Q

decay series

A

if the daughter nuclei produced are unstable and they continue to decay until a stable isotope is formed

51
Q

define nuclear fusion

A

two lighter nuclei joining together to form a heavier nucleus + releasing lots of energy

52
Q

what element does nuclear fusion always happens between the isotopes of?

A

hydrogen

53
Q

are the products of nuclear fusion radioactive?

A

no, the products of nuclear fusion are not radioactive (unlike fission)

54
Q

explain the difference between nuclear fission and nuclear fusion (6 marks)

A

-big nuclei split up in fission; small nuclei join together in fusion ;

-fission can take place at normal temperatures and pressures, but fusion needs high temperatures and pressures

-fission creates radioactive waste while fusion does not.

55
Q

state three advantages of fusion over fission

A

-fusion releases more energy, per 1kg of fuel
-less radioactive emissions
-uses cleaner fuel - can be sourced from water

gcse physics (3 decks)

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