I dont understand this problem. Will somebody please help me out with this chemistry!!!?

The radioactive isotope Thallium-201 (201Tl) is used in medical diagnosis and treatment. A gamma ray emitted by an atom of 201Tl has an energy of 0.167 MeV. (1 MeV is 1 x 106 eV and 1 eV = 1.6022 x 10-19 J). What is the frequency in Hz of this gamma ray?