Flashcards in Inverse square law for gamma radiation Deck (5)
○ Gamma source
○ Geiger counter
○ Metre ruler
○ With the geiger counter far from the gamma source, start the
stopwatch and geiger counter and after 20 minutes, record the
total count reading. This is the background
○ Bring the source into the laboratory and set the distance X
between the geiger counter and the gamma source to 0.600m,
measured using the metre ruler. Start the stopwatch and geiger
counter and take the count N after 5 minutes.
○ Reduce X by 0.100m and repeat this, reducing it by 0.100m each
time down to 0.100m.
○ Repeat the experiment twice more and find and record the mean C
for each X.
Graphs and calculations
○ Calculate and tabulate the count rate C for each X using C=N/t and
do the same to find the background count rate. Then calculate and
tabulate the corrected count rate C’ by subtracting the background
count rate from C.
○ Plot a graph of 1/√C’ against X which should give a straight line,
verifying the inverse square law.
○ Exposure to radiation can destroy cells or cause mutations.
Therefore, you should keep as big a distance between you and
the source as possible, only keep the radioactive source out of its
lead-lined container for as long as the experiment takes and
handle it only with tongs and do not allow it to touch your skin.