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→Finding Half Life from a Graph
===Finding Half Life from a Graph===
{| class="wikitable"
|-
|[[File:HalfLifeGraph2.png|center|300px]]
|[[File:HalfLifeGraph3.png|center|300px]]
|-
| style="height:20px; width:300px; text-align:center;" |Find the '''half life''' from this [[graph]].
| style="height:20px; width:300px; text-align:center;" |Find the '''half life''' from this [[graph]].
|-
|[[File:HalfLifeGraph2b.png|center|300px]]
|[[File:HalfLifeGraph3b.png|center|300px]]
|-
| style="height:20px; width:300px; text-align:center;" |There is 100% of the [[isotope]] at the beginning. Draw a horizontal line from 50% to the curve. Draw a vertical line down from the curve to indicate the '''half life'''.
'''Half Life''' = 4 [[minute]]s
| style="height:20px; width:300px; text-align:center;" |The [[Count Rate|count rate]] began at 70,000Bq. Draw a horizontal line from 35,000 (half the initial count rate) to the curve. Draw a vertical line down from the curve to indicate the '''half life'''.
'''Half Life''' = 6 [[hour]]s
|}
===Calculating Half Life===
{| class="wikitable"
|-
| style="height:20px; width:300px; text-align:center;" |An [[isotope]] had a [[Count Rate|count rate]] of 200Bq and 90 days later has a [[Count Rate|count rate]] of 25. Calculate the '''half life''' of this [[isotope]].
| style="height:20px; width:300px; text-align:center;" |A [[radioactive]] [[sample]] begins with 224 [[atom]]s of an [[Unstable Isotope|unstable isotope]] 18 [[minute]]s later there are only 14 [[atom]]s of the [[Unstable Isotope|unstable isotope]] left. Calculate the '''half life''' of this [[isotope]].
|-
| style="height:20px; width:300px; text-align:center;" |'''1. Identify how many times the [[Count Rate|count rate]] has halved.'''
<math>200 \div 2 = 100<math>
<math>100 \div 2 = 50<math>
<math>50 \div 2 = 25<math>
The [[Count Rate|count rate]] has halved 3 times.
| style="height:20px; width:300px; text-align:center;" |'''1. Identify how many times the number of [[Unstable Isotope|unstable]] [[atom]]s has halved.'''
<math>224 \div 2 = 112<math>
<math>112 \div 2 = 56<math>
<math>56 \div 2 = 28<math>
<math>56 \div 2 = 28<math>
The number of [[Unstable Isotope|unstable]] [[atom]]s has halved 4 times.
| style="height:20px; width:300px; text-align:center;" |'''2. Divide the time taken by the number of times the [[Count Rate|count rate]] has halved.'''
<math>90 \div 3 = 30<math>
'''Half Life''' = 30 days.
| style="height:20px; width:300px; text-align:center;" |'''2. Divide the time taken by the number of times the number of [[Unstable Isotope|unstable]] [[atom]]s has halved.'''
<math>18 \div 4 = 4.5<math>
'''Half Life''' = 4.5 [[minute]]s
|}
===Finding Half Life and Count Rate from a Table===