$2)$ A $2\mathrm{.}5$ MeV gamma ray is emitted by a nuclear source. a$)$ What is the wavelength of the photon? b$)$ The gamma ray scatters off of a free electron, the new wavelength of the light is $1$e$-12$m$.$ What is the momentum of the recoiling electron? $($The mass of an electron is $511,000$ eV$/$c$2.$ Put your answer in terms of eV$/$c$.)$ c$)$ Suppose the electron has a recoil momentum of $1\mathrm{.}2$ MeV$/$c$.$ What is it$$s de Broglie wavelength?