An electron of mass m and a photon have same
energy E. The ratio of de-Broglie wavelengths
associated with them is :
(1)``\frac 1c(\frac{E}{2m})^\frac 12``
(2)``(\frac{E}{2m})^\frac 12``
(3) ``c(2mE)^\frac 12``
(4) ``\frac {1}{xc}(\frac{2m}{E})^\frac 12``
(c being velocity of light)