Answer. com after three half-lives, what fraction of a radioactive sample has decayed?

Thus the fraction decayed is

Explanation: Radioactive decay follow first order kinetics.

Now, to calculate the amount decayed after n half lives, we use the formula:

where,

a = amount of reactant left after n-half lives

= Initial amount of the reactant

n = number of half lives  = 3

Putting values in above equation, we get:

The fraction decayed after 3 half lives will be of the initial amount.

Thus the fraction decayed is

a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.