Question

If the half life of a radioactive isotope is 1 day, then how much of the original isotope remains at the end of two days?

Answer 1

$\huge{\color{magenta}{\fcolorbox{magenta}{black}{\huge{\color{white}{\fcolorbox{aqua}{black}{✿ᴀɴsᴡᴇʀ✿}}}}}}$

25%

Explanation:

In a half life of a radioactive isotope is 1 day,it means it loses its half mass each day

We a formula for N half life

$\sf { \frac{1}{2} }^{n}$

where n is the number of days

Here the isotope is kept for 2 days

so it's left over mass will be

$\sf { (\frac{1}{2}) }^{2} \\ \\ \\ \frac{1}{2} \times \frac{1}{2} \\ \\ \sf \frac{1}{4}$

It's left over mass 1/4th of the original mass

Now, we need to find it's percentage by multiplying with 100

$\sf \frac{1}{4} \times 100 \%\\ \\ \sf \cancel\frac{100}{4} \% \\ \\ \sf 25\%$

So 25% mass will be left after 2 day of half life radioactive isotope.

Answer 2

25% because the half life of 100 is 50 and the half life of 50 is 25