Question

Accumulation of Stable Atoms

A graph with number of half-lives on the x-axis from 0 to 10 and number of radioactive atoms from 0 to 100. A green line is a quadratic curve aching up from the origin. The orange graph is a curve starting at the origin and curves up to (10, 100), a mirror image of the green graph. There is a purple line from (0, 100) to (10, 0). There is a blue line starting at (0, 100) and is an inverse curve down.

Which line on the graph represents the accumulation of stable atoms during the decay of a radioactive substance?

the blue line
the orange line
the green line
the purple line

Answer 1

The orange line.

Reason: Stable atoms start at 0 and increase toward 100 as radioactive atoms decay. If radioactive atoms follow an exponential decay (the blue curve), the stable count is 100 − (radioactive), giving a curve that starts at 0 and rises quickly then levels off (concave down) — the orange curve.