azra radioactive decay
TRANSCRIPT
RADIOACTIVE DECAYby : azyulail azra
radioactivity
• cannot be detected.
• energetic enough to knock electrons out of the atoms of a medium to produce ions.
• also known as ionising radiation.
The spontaneous disintegration of an unstable nucleus
particles
photons
emission of energetic
radioactive emissions
α-particleshelium nucleus
γ-rayselectromagnetic
waves
γ-raysβ-particlesα-particles
differencesCharge Positive
chargeNegative charge
No charge (neutral)
Speed Up to 10% of speed of light
Up to 99% of speed of light
Speed of light
Nuclide notation
-He42 e
0
-1
Penetratingpower
# Low# Stopped by a sheet of paper
# Average# Stopped by a fewmillimeters ofaluminium
# High# A few centimetersof lead can absorb a significantamount of it
γ-raysβ-particlesα-particles
Effect of magnetic field
Small deflection
Largedeflection in the opposite direction of the α-particles
Nodeflection
γ-raysβ-particlesα-particles
Effects of electric field
Small deflection towards negatively charged plate
Largedeflection towards positively charged plate
No deflection
γ-raysβ-particlesα-particles
Range in air
Several centimetres
Several metres
Several hundred metres
Tracks in cloud chamber
Straight and thick lines
Thin and wavy lines
Very fine short lines
Ionising power
Strong Medium Very weak
γ-raysβ-particlesα-particles
radioactive detectors
Cloud chamberGeiger-Muller TubeSpark counter
Photographic Film
cloud chamber
- to show the path of ionizing radiation.
- formed in the same way as the
condensation trails behind a high-flying aeroplane
α - particles β - particles γ - rays
photographic film- Found in badges worn by the staff at
radiation laboratories
GM tubeRadiation Enters through
mica window
Ionizes argon gas
Pulse of current
produced Pulse of current counted using
ratemeter/scaler
Number of counts
period of time
240 V
spark counter
radioactivesource is brought near
ionizes the air
between the gauze and the
wire
sparksare produced
Suitable for alpha rays
radioactive decay• Nuclei that have too few or too many neutrons are
most likely to be unstable.
• the process of a nucleus changing to a more stable nucleus while emitting radiation.
• Nucleus before the decay = parent nuclideproduct of the decay = daughter nuclide.
• The daughter nuclide may still be unstable and will eventually decay into another nuclide.
• This process continues until a stable nuclide is reached.
Alpha decay-This type of decay usually happens to the heavier unstable nuclei.
-The proton number is reduced by 2 while the nucleon number is
reduced by 4 and emit α-particles
U23892 He4
2Th +238 – 4 = 23492 – 2 = 90
Beta decay-Beta decay usually occurs for nuclei that have an
excess of neutrons.
- There is no change in the nucleon number but the
proton number increases by 1and emit β-particles
C14
6 e0-1N +14 - 0 = 14
6 - (-1) = 7
Gamma decay-occurs when an unstable nucleus releases its excess energy [ high
frequency electromagnetic waves ] called γ-rays.
-no change in proton number and
nucleon number but emit γ-rays-A nucleus that undergoes alpha or beta
decay may also emit γ-rays.
Co60
27 γCo +60
27
half-life
• Time taken for undecayed nuclei to be reduced to half of its original number
• The number of unstable nuclei have not decayed decreases with time.
• The half-life constant ~ the decay process is random and large.
Original number of
undecayed nuclei
Half of original number = 128
= 256It takes 3 hours for the undecayed nuclei to be reduced to half of original number.
∴ 1 half-life = 3 hours
64
128
Radionuclide Half-life (T1/2)90Sr Strontium-90 28.5 years
137Cs Caesium-137 30.1 years226Ra Radium-226 1600 years
14C Carbon-14 5736 years40K Potassium-40 1.28 x 108
years
Thank you !!!