Radioactive isotopes are used to a. determine the absolute age of rocks. c. determine how rocks are formed. b. determine the relative age of rocks. d. determine how rocks are changed. select the best answer from the choices provided a b c d

a. determine the absolute age of rocks.

Explanation: Radioactive isotopes being unstable decay by emitting particles and the rate of disintegration at any time depends on the number of atoms of the radioactive isotope present at that time.

Hence radioactive decay follows first order kinetics.Thus, if atoms of radioactive isotope are present initially and N atoms are present after time t, then

Rate of disintegration at time t

where k= disintegration constant

The expression used to calculate the absolute age is:

where,

k = rate constant

t = time taken for decay process

a = initial amount of the reactant

a - x = amount left after decay process

c.the charges if the proton and electron and gravity

heat the gas and measure the pressure