<h2>
Answer: The half-life of beryllium-15 is 400 times greater than the half-life of beryllium-13.</h2>
Explanation:
The half-life 
of a radioactive isotope refers to its decay period, which is the average lifetime of an atom before it disintegrates.
In this case, we are given the half life of two elements:
beryllium-13: 
beryllium-15: 
As we can see, the half-life of beryllium-15 is greater than the half-life of beryllium-13, but how great?
We can find it out by the following expression:
Where 
is the amount we want to find:
Finally:
Therefore:
The half-life of beryllium-15 is <u>400 times greater than</u> the half-life of beryllium-13.
To be considered a source of water pollution, the source must include a chemical is false.
<u>Explanation:
</u>
The water pollution may be caused either by chemicals or waste materials that doesn’t contain chemicals such as domestic wastes, organic compounds, heavy metals etc. The life on Earth mostly relies on water and air, and if these two gets polluted; the results will be dangerous.
Around 70% of the planet is covered with water and the present state of its purity is a matter of a serious thought. Looking over various pollutants, only chemical wastes are not responsible to pollute the water.
Instead, there is range of elements from plastic scraps to chemical wastes that comes from either the non-point sources or the point sources. There are organic waste materials, heavy metals, volcanic eruptions, Tsunamis, earthquakes, etc. are also responsible to contaminate water and affect the amphibians as well as humans.
If the object is kept in between the principle axis and the focus but some what nearer to the focus then we will get the enlarge,erect,and real image.
To verify the identity, we can make use of the basic trigonometric identities:
cot θ = cos θ / sin θ
sec θ = 1 / cos <span>θ
csc </span>θ = 1 / sin θ<span>
Using these identities:
</span>cot θ ∙ sec θ = (cos θ / sin θ ) (<span> 1 / cos </span><span>θ)
</span>
We can cancel out cos <span>θ, leaving us with
</span>cot θ ∙ sec θ = 1 / sin θ
cot θ ∙ sec θ = = csc <span>θ</span>
