P7 : Radioactivity Flashcards
What is Brownian motion?
- random motion of tiny particles in a fluid
Who and what was the nuclear model first discovered?
JJ THOMPSON
- electrons were thoughts to be embedded in a positively charged lump of mass
-PLUM PUDDING MODEL
What did RUTHERFORD discover about the structure of atoms?
- most alpha particles went through GOLD FOIL
- HE FOUND most particles PASSED straight through foil - shows atom is EMPTY SPACE
-small no. alpha particles DEFLECTED TO SIDE - shows + charge located in small space
- some particles bounced straight back - suggest + charge/mass is CONCENTRATED IN SAMLL SPACE
WHAT was Rutherford’s conclusion after gold foil experiment?
- atom is like a solar system
- most mass/+ charge in small space in centre
- electrons orbit around centre
How did they discover NEUTRONS?
JAMES CHADWICK
- knew that mass of nucleus is bigger than tootle mass of protons , so must be UNCHARGED TWIN
- THE NEUTRON
what is a nuclide ?
a nucleus with different no. NEUTRONS
what does it mean by ‘radioactive’?
- they are UNSTABLE and give out RADIATION at random intervals IN A PROCESS CALLED ‘RADIOACTIVE DECAY’
- radioactivity is random - decay happens with a CERTAIN PROBABILITY
What is the amount of RADIOACTIVE DECAYS PER SECOND called ?
the ACTIVITY of a sample
- measure in BECQUERELS (Bq)
2 ways to detect RADIOACTIVITY?
GEIGER MULLER TUBE
PHOTOGRAPHIC FILM
what is alpha radiation?
- atoms decay INTO NEW TYPE OF ATOM and EMITS APLHA PARTICLE
- Alpha particles have 2 protons/2 neutrons ( HELIUM ATOMS)
- ALPHA happens when nucleus HAS TOO MANY PROTONS
what is BETA radiation?
- when NEUTRON turns into PROTON/ELECTRONS
-fast moving , high energy electron is called a BETA PARTICLE - Beta happens when NUCLEUS HAS TOO MANY NEUTRONS
what is GAMMA RADIATION?
- very high energy LIGHT , with very high FREQUENCY , VERY SHORT WAVELENGTH
- atom IS NOT changed by emitting light
- Gamma happen when parent nucleus has too MUCH electromagnetic energy
what is the charge, mass , penetration ability, range in air, and ionising ability of ALPHA, BETA AND GAMMA?
ALPHA. BETA GAMMA
+2. -1 0
4 0 0
LOW MEDIUM. HIGH
few cm 1m infinite
high. medium low
what is HALF LIFE?
- time taken for Half of the radioisotopes in a sample to DECAY.
how is a radiation used in MEDECINE?
TRACERS
small amounts of radioactive material used to detect GAPS OR BLOCKAGES
Gamma used bc of low ionising ability and high penetration ability
- SHORT HALF LIFE
RADIOTHERAPY
- high energy gamma radiation can be used to destroy cancer cells, but have to make sure it doesn’t damage other tissues
what is SPONTANEOUS FISSION?
very large nuclei need extra NEUTRONS to stop PROTONS from repelling nucleus apart
what is INDUCED FISSION?
can be made to split up by absorbing a NEUTRON , destabilising the nucleus , causing it to SPLIT IN HALF.
WHAT IS FUSION?
under extremely high temps/pressure , tow protons can be fused together - continue until helium is made
what is nuclear fission?
the splitting of a large, unstable nucleus into two smaller nuclei
what is count rate?
number of decays recorded each second by a detector.
explain the process of nuclear fission. (4)
- neutrons are absorbed by a nucleus
- nucleus splits into 2 daughter nuclei
- releasing gamma rays
- and 2/3 neutrons
Why is does the food not become become radioactive after being irradiated?
- because it only come in contact with radiation not with isotope itself
Ways to protect against radiation?
- lead apron
- gloves for alpha
- lead walls
- radiation monitor can measure how much is received by person
Why is radiation contamination dangerous ?
- the radioactive isotopes end up on materials so becomes RADIOACTIVE
- they decay and emit ionising radiation
What is meant by precise results?
- how close measurements are (small variation in results)
Name or nuclear fuel
Uranium
How does the process of nuclear fusion lead to release of energy?
Lighter nuclei form heavier nuclei
Some mass converted to energy
Advantage of radioactive waste having shorter half life
Activity decreases quickly
- risk of harm decreases quickly
why take repeat reading ?
- calculate mean
- reduce effect of random errors
risk of short harlf life?
- nuclei will decay very quickly, emiitting alot of radiation in short period of time (COUNT RATE DECREASES QUICKLY)
benefit and risk of long half life?
BENEFIT : decay slowly, so not asmuch radiation emitted (COUNT RATE IS CONSTANT)
RISK - remain radoactive for long time , so more risk of contamination
