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Finding half-life from a graph half-life The half-life in this example is about 30 seconds. A more accurate value can be obtained be repeating this method for a other initial nuclei numbers and then taking an average.
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Do Now Copy and complete : page 265
The ________ of a radioactive substance is the average time taken for half of the _______of the substance to decay. It is also equal to the average time taken for the ________ of the substance to halve.
The half-life of carbon 14 is about _______ years. If today a sample of carbon 14 has an activity of 3400 Bq then in 5600 years time this should have fallen to ______ Bq. 11200 years later the activity should have fallen to ____ Bq.
The number of carbon 14 nuclei would have also decreased by ______ times.
eight half-life5600 425 activity1700
WORD & NUMBER SELECTION:
nuclei
eight
half-life
5600
425
activity
1700
nuclei
Today’s lesson• Find the half life from graphs version 2.
• Give and explain examples of practical applications of isotopes.
Title Uses of radioactive isotopes
Finding half-life from a graph
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600
0 20 40 60 80 100 120
time (seconds)
num
ber
of n
ucle
i
half-life
The half-life in this example is about 30 seconds.
A more accurate value can be obtained be repeating this method for a other initial nuclei numbers and then taking an average.
Question 6
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800
900
0 10 20 30 40 50 60 70 80 90 100
time (seconds)
activ
ity (B
q)
Estimate the half-life of the substance whose decay graph is shown opposite.
half-life
Revision SimulationsHalf-Life - S-Cool section on half-life and uses of radioactivity including an on-screen half-life calculation and an animation showing thickness control.
BBC AQA GCSE Bitesize Revision: Detecting radiation Natural sources of background radiation Artificial radiation Half life
Alpha Decay - PhET - Watch alpha particles escape from a Polonium nucleus, causing radioactive alpha decay. See how random decay times relate to the half life.
TitleUses of radioactive isotopes
Smoke detection
• Uses
Thickness control
Thickness control
Used as Tracers
Used as Tracers
Killing microbes
Killing microbes
Checking welds
Used as Tracers
Carbon dating
“Can you………?”
• Bring in your exercise books on
Thursday 27th Sept.
Test!
Thursday 27th September 2012
I will collect your Exercise books on Thursday – Remember them!
Can you answer the all the questions on
pages 265 and Q5,7,8,9 &10 page
270?
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