Eight minutes later the count rate is 1200 counts per

Question

1. A Geiger counter registers a count rate of 4,800 counts per minute from a sample of a radioisotope. Eight minutes later, the count rate is 1,200 counts per minute. What is the half-life of the radioisotope?
2. Gamma rays (γ-rays) are high-energy photons. In a certain nuclear reaction, a γ-ray of energy 0.685 MeV(million electronvolts) is produced. Compute the frequency of such a photon