radioactivity

Question 1

explain how energy can be transferred mechanically and electrically

Answer 1

• when gravity accelerates an object + gives it KE + TE

- when a current passes through a lamp + emits light and heat

Question 2

examples of energy

Answer 2

KE
GPE
chem (food + battery)
elastic (springs + rubber)
Electrical
Heat/radiation
electrostatic
nucleur

Question 3

describe alpha radiation

Answer 3

helium nucleus
2 protons, 2 neutrons

• most ionizing
• least penetrating
• stopped by sheet of paper

Question 4

describe beta radiation

Answer 4

• stopped by thin sheet aluminum

- moderately ionizing/penetrating

Question 5

describe gamma radiation

Answer 5

• highest penetrating
• lowly ionizing
• stopped by many cm of lead

Question 6

Steps for decay calculation

Answer 6

1. determine activity e.g 2000bq is 2000 nuclei decay per second
2. determine time period in s ( x x 60s)
3. multiply activity x time period

Question 7

describe radioactive decay + define half-life

Answer 7

• spontaneous and unstable to a stable nucleus

- time is taken for half the sample to decay

Question 8

ways of detecting radiation

Answer 8

• Geiger Muller tube
• each time it absorbs radiation - transmits electrical impulse to machine
• produces clicking sound —> frequency of pulses
• the greater the frequency of clicks= more radiation present

Question 9

sources of background radiation: externally detected weak sources of radiation

Answer 9

from space: cosmic rays high energy particles penetrating atmosphere

from earth:

• radioactive rocks release radon gas
• medicals sources - x rays//MRI’s

Question 10

uses of alpha radiation

Answer 10

smoke detectors

long-half alpha particles create a current in alarm

if smoke enters, alpha particles are absorbed = current drops triggering alarm

Question 11

uses of gamma radiation

Answer 11

sterilization of equipment/tracers for diagnosis/destroy tumors

gamma emitters kill bacteria -safe for surgery

short-half gamma emmiters used as tracers in certain parts in body.

Question 12

steps for half life calc

Answer 12

1. Count number of un-decayed atoms that halved

2. time period/number of half-lives

Question 13

contamination vs irradiation

Answer 13

• unwanted presence of materials containing radioactive atoms
• becomes radioactive + emits
• prevention = safe handling
• the process of exposing a material to alpha, beta or gamma radiation
• method of sterilization to kill living cells = not make radioactive
• prevention = shielding like lead clothing

Question 14

how do smoke alarms work

Answer 14

• radioactive subs in alarm emits alpha radiation = ionizes air in detector
• current flows between plates —> smoke interferes w radiation
• air no longer ionized = no current flow
• reduction in current flow —-> triggers alarm

Question 15

when alpha decay occurs what happens to atomic + mass number

Answer 15

• atomic number dcreases by 2
• mass number decreases by 4
• new element formed

Question 16

what effect does emitting gamma radiation have on mass + atomic number

Answer 16

• none

Question 17

what effect does beta minus decay have on atomic + mass number

Answer 17

• mass number = same

- atomic number increases by one

Question 18

uses of beta radiation in tracers or gamma same thing

Answer 18

• tracer inserted in body = targets specific parts of body e.g cancerous cells
• tracer emits beta radiation —> detected by external machines