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RADIOACTIVE
DECAY
by : azyulail azra
radioactivity
particles
emission of
energetic

The spontaneous

disintegration of
an unstable nucleus

photons
• cannot be...
radioactive emissions
α-particles
helium nucleus

γ-rays
electromagnetic
waves
differences
α-particles β-particles
Charge

Positive
charge

Speed

Up to 10% Up to 99% Speed of
of speed of of speed of l...
Penetrating

power

γ-rays
α-particles β-particles
# Average # High
# Low
# Stopped by # Stopped by
a few
a sheet of
milli...
α-particles β-particles
Effect of
magnetic
field

Small
deflection

γ-rays

Large
No
deflection deflection
in the
opposite...
α-particles β-particles
Effects of
electric
field

Small

Large

deflection
towards
negatively
charged
plate

deflection
t...
α-particles β-particles

Range
in air

Several
centimetres

Several
metres

γ-rays
Several
hundred
metres

Tracks in Strai...
radioactive detectors

Cloud chamber
Photographic Film
Geiger-Muller Tube
Spark counter
cloud chamber
- to show

the path of ionizing radiation.
- formed in the same way as the

condensation trails behind
a hig...
α - particles

β - particles

γ - rays
photographic film
- Found in badges worn by the staff at

radiation laboratories
GM tube
Radiation

Enters through
mica window

240 V

Ionizes
argon gas
Pulse of
current
produced

Pulse of current
counte...
spark counter

Suitable for alpha rays

ionizes
the air
between the
gauze and the
wire

radioactive
source is
brought near...
radioactive decay
• Nuclei that have too

few or too many neutrons are

unstable.
the process of a nucleus changing to a
m...
Alpha decay
-This type of decay usually
happens to the heavier

unstable nuclei.
-The proton number is reduced by

2 while...
14

6C

14 - 0 = 14
N
6 - (-1) = 7

+

0
-1

e
Beta decay
-Beta decay usually occurs
for nuclei that have

an
excess of
ne...
Gamma decay
-occurs when an unstable nucleus
releases its excess energy [ high

frequency electromagnetic
waves ] called γ...
half-life
• Time taken for undecayed nuclei to be
reduced to half of its original number
• The number of unstable nuclei h...
128
64

Original number of
undecayed nuclei

= 256

Half of original number = 128

It takes 3 hours for the
undecayed nucl...
Radionuclide

Half-life (T1/2)

90Sr

Strontium-90

28.5 years

137Cs

Caesium-137

30.1 years

226Ra

Radium-226

1600 ye...
Thank
you !!!
Azra radioactive decay
Azra radioactive decay
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Azra radioactive decay

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Azra radioactive decay

  1. 1. RADIOACTIVE DECAY by : azyulail azra
  2. 2. radioactivity particles emission of energetic The spontaneous disintegration of an unstable nucleus photons • cannot be detected. • energetic enough to knock electrons out of the atoms of a medium to produce ions. • also known as ionising radiation.
  3. 3. radioactive emissions α-particles helium nucleus γ-rays electromagnetic waves
  4. 4. differences α-particles β-particles Charge Positive charge Speed Up to 10% Up to 99% Speed of of speed of of speed of light light light Nuclide notation 4 He 2 Negative charge γ-rays 0 -1 e No charge (neutral) -
  5. 5. Penetrating power γ-rays α-particles β-particles # Average # High # Low # Stopped by # Stopped by a few a sheet of millimeters of paper aluminium # A few centimeters of lead can absorb a significant amount of it
  6. 6. α-particles β-particles Effect of magnetic field Small deflection γ-rays Large No deflection deflection in the opposite direction of the αparticles
  7. 7. α-particles β-particles Effects of electric field Small Large deflection towards negatively charged plate deflection towards positively charged plate γ-rays No deflection
  8. 8. α-particles β-particles Range in air Several centimetres Several metres γ-rays Several hundred metres Tracks in Straight and thick cloud chamber lines Thin and Very fine wavy lines short lines Ionising power Medium Strong Very weak
  9. 9. radioactive detectors Cloud chamber Photographic Film Geiger-Muller Tube Spark counter
  10. 10. cloud chamber - to show the path of ionizing radiation. - formed in the same way as the condensation trails behind a high-flying aeroplane
  11. 11. α - particles β - particles γ - rays
  12. 12. photographic film - Found in badges worn by the staff at radiation laboratories
  13. 13. GM tube Radiation Enters through mica window 240 V Ionizes argon gas Pulse of current produced Pulse of current counted using ratemeter/scaler Number of counts period of time
  14. 14. spark counter Suitable for alpha rays ionizes the air between the gauze and the wire radioactive source is brought near sparks are produced
  15. 15. radioactive decay • Nuclei that have too few or too many neutrons are unstable. the process of a nucleus changing to a more stable nucleus while emitting most likely to be • radiation. • Nucleus before the decay = parent product of the decay • • nuclide = 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.
  16. 16. 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 αparticles 238 92 U 238 – 4 = 234 92 – 2 = 90 Th + 4 2 He
  17. 17. 14 6C 14 - 0 = 14 N 6 - (-1) = 7 + 0 -1 e 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 1 and emit β-particles
  18. 18. 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 60 Co 27 also emit γ-rays. 60 27 Co + γ
  19. 19. 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.
  20. 20. 128 64 Original number of undecayed nuclei = 256 Half of original number = 128 It takes 3 hours for the undecayed nuclei to be reduced to half of original number. ∴ 1 half-life = 3 hours
  21. 21. Radionuclide Half-life (T1/2) 90Sr Strontium-90 28.5 years 137Cs Caesium-137 30.1 years 226Ra Radium-226 1600 years 14C Carbon-14 5736 years 40K Potassium-40 1.28 x 108 years
  22. 22. Thank you !!!

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