Radioactive isotopes are used to determine the (absolute/relative) age of rocks.

Radioactive isotopes are unstable and will decay. For example, when humans die carbon-14 decays. The isotopes will decay into a stable isotope over time. Scientists can tell how old the rock was from looking at the radioactive isotope's half-life, which tells them how long it would take for there to be half the radioactive isotope and half the stable isotope. At the next half-life there will be 25% of the radioactive isotope and 75% of the stable isotope. At the next half life there will be 12.5% radioactive and 87.5% stable.

Answer;

Absolute age of rocks

Explanation;Relative age of a rock refers to the age of a rock layer compared to other layers, while absolute age is the numeric age of a layer of rocks or fossils. Radioactive isotopes are used to determine the absolute age of rocks.For example, radioactive isotopes are used to determine the absolute age of igneous rock by determining how much parent or daughter is left and that determines the age; meteorites