A radioactive isotope emits radiation at the rate of 32 microwatts at one instant of time. after one hour, it emits radiation at the rate of 2 microwatt.

A radioactive isotope emits radiation at the rate of 32 microwatts at one instant of time. After one hour, it emits radiation at the rate of 2 microwatt. The half life of the isotope is hours. [Give the answer in 2 decimal places