An electron of mass m and a photon have same energy E. The ratio of de-Broglie wavelengths associated with them is

For electron of energy  E de-Broglie wavelength, λe=hp=h2mEFor photon of energy,E=hv=hcλp⇒λp=hcE∴λeλp=h2mE×Ehc=1cE2m1/2