physics Flashcards
what are the 3 types of radiation
alpha, beta, gamma
what is the charge of alpha
2 neutrons
2 protons
(+2)
What is radioactive decay
A neucleus emitting radiation to make it more stable
What is beta radiation, and how is it produced
single electron
produced in nuclei when a neutron changes into a proton and an electron
What is gamma radiation
gamma radiation is an electromagnetic wave
How do these radiations penatrate and ionise differently
Alpha - least penetrative (stopped by a peice of paper)
->very ionising (highest mass and charge)
Beta - goes through paper, but stopped by thin aluminium
->ionising
Gamma - can only be partially stopped by lead (goes through rest)
->weakly ionising
When an alpha particle in emmited, how does it affect the mass number and atomic number
mass number +4
atomic number +2
When an beta particle in emmited, how does it affect the mass number and atomic number
mass number stays the same
atomic number +1
WHat neucleus does an alpha particle have?
Helium
What is th mass of an alpha particle
4 x the mass of neucleon
what is the mass of a beta particle
1/2000 mass of a proton
Whats the mass of a gamma ray
massless
Describe the penetration through air of alpha, beta and gamma particles
alpha: a few cms
bta: several metres
Gamma: long range
What is ionisation?
-Ionisation is when radiation of high energy passes through matter, and can knock electrons out of atoms
-this creates free electrons and positively charged ions
What is ionisation useful for?
-detecting radiation e.g GM tubes and cloud chambers
How is ionisation pottentially damaging
can kill living cells causing mutations or possibly cancers
What is a half-life
-> Time taken for activity of a parents smaple of neuclei to half it’s original level
Different isotopes have different half lives
How do you measure half-lives?
-measure initial activity, Ao of the sample
-determine half life of this original activity
-measure how activity changes with time
number of parents neuclei half
mass of radioisotope present to reduce by half
activity of sample to reduce by half
look at worked example - save my exams
Name 5 uses of radioactivity
-Smoke detectors
-monitoring thickness of material
-sterilising food/medical equipment
Explain how smoke detectors use alpha rays
-alpha will ionise air within smoke detector, causing a current
-alpha emmiter is blocked when smoke enters detector
-alarm is triggered when sensor no longer detects alpha
What is contamination?
The accidental transfer of a radioactive substance onto or into a material
What is irradiation?
The process of exposing a material to ionising radiation, but not in contact with it
2 isotopes of the same element
Same number of protons different number of electrons
Atomic number
the number of protons in the neucleus of an atom
mass number
the number of neucleons (protons+neutrons) in a neucleus
Background radiation
ionising radiation from earth and space (rocks, food, cosmic rays)
What is activity
number of decays per second (Bq)
How does the geiger meter work?
The Geiger-Muller tube is a device that detects radiation.
It gives an electrical signal each time radiation is detected. These signals can be converted into clicking sounds, giving a count rate.
(in clicks per second or per minute)
