Hi, I've read that the frequency of EMR is found by means of a spectroscope , which uses diffraction grating and that it is derived indirectly from its wavelength. Is that true? Is there a way, an instrument that count directly the frequency of a photon or a y-ray? and up to what frquency? Is it possible to verify that the frquency of a γ-ray resulting from the annihilation of an electron is 1.2356 x 10^20 Hz (511.000 eV)? Thanks for your help!