It seems that you did not provide possible answers, but the mark recapture method is one method that is not very invasive. The population size is estimated by marking a certain number of individuals and releasing them into the wild, followed by a second capture later on. The members captured the second time with the markets from the original capture are used to estimate population size in the formula s*n/x where s and n are the first and second captured population sizes and x is the number of marked inidividuals from the second capture.
To calculate this we will use the light equation:

λ

We have Frequency

.
We know that speed of light in vacuum is

.
Since a unit of speed of light is m/s, we can change the unit of frequency Hz to 1/s, since Hz means cycles per second (f=1/T).
So:

<span>

</span>
<span>

λ

</span>⇒ λ

⇒ λ

⇒ <span>λ</span>
One of the most important reasons for only using reliable water source is to reduce : Infections
Without laboratory testing, it is impossible to actually known what type of contamination that a water source have.
For
all we know, a water source could contaminated with chemicals or
bacteria that could caused internal infections within our body