4. Discussion

4.1 Key findings & Analysis of results
The Results were inconsistent, some reasons are that the amount of time spent in biosafety cabinet too long, or the pond water quality was sometimes too clean and other times too dirty. The position of the object (tissue) to block the UV rays from the control setup is set up is different for a few times. we could not deduce consistent enough results to prove our hypothesis is 100% correct but from our most consistent result we can tell that UV light has a high chance of killing bacteria after 100 seconds of exposure to UV rays.


4.2 Explanation of key findings
The number of bacteria in the pond was varying from time to time as we took our samples. Some times,
the pond water was murkier than others and thus had more bacteria. Therefore, our results were inconsistent
due to the different number of bacteria in the sample each time. The UV light is strong enough to destroy all
bacteria after at least 100 seconds. After 100 seconds, there was no observable trace of bacteria, this means
that a duration of 100 seconds is strong enough to wipe out all bacteria.


If the bacteria is exposed to UV light for 40 seconds or less, unobservable changes in the bacteria number.


If the bacteria is exposed to UV light for 100 seconds or more, the bacteria have been completely eradicated by the UV ray.


If the bacteria is exposed to UV light for 60-80 seconds there is a slight decrease in the amount of bacteria in the petri dish


4.3 Evaluation of Hypothesis
We cannot prove if our hypothesis is right or wrong as our results were very inconsistent and we could not
anticipate the number of bacteria in the different pond water samples and what blocks the UV light for our control.
However, we can conclude that UV light is still strong enough to kill bacteria as when we did the experiment for
80 secs, 100 secs and 120 secs, there was still bacteria at 80 secs while after 100 seconds there was no more
bacteria in the sample,thus, our hypothesis is considered right as the UV light did kill bacteria, just that it takes
quite an amount of time. Whereas 20 seconds to around 60 seconds, UV light is not able to kill all bacteria as
we experimented the first time and it failed. We decided to repeat the experiment but there was still bacteria, so
we can conclude that UV light has a high chance of not destroying all bacteria in 20 to 60 seconds. It could also
be the fact that the UV rays were not strong enough to kill the bacteria.


4.4 Limitations and Areas for improvement


We could increase the number of setups using the same sample pond water to make the amount of bacteria per
setup more consistent. We can also choose a pond which is not going through major changes in a short amount
as the number of bacteria would be more consistent and make our result more encouraging. But If the results are
not consistent, we can repeat the experiment but with different timings and look at the results again. As sometimes
the number of bacteria is so big that we can't count and other times the number is so small that we also cannot
count it. Thus we are unable to form a graph and instead made a table. We could have better researched on
what easily accessible item blocks out UV rays properly so as to not guess, as we had guessed that tissue
blocks out UV rays and used that to block for our control.

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