An electron (of mass $m$) and a photon have the same energy $E$ in the range of a few eV. The ratio of the de Broglie wavelength associated with the electron and the wavelength of the photon is ($c =$ speed of light in vacuum)\\
(1) $\frac { 1 } { c } \left( \frac { 2 E } { m } \right) ^ { 1 / 2 }$\\
(2) $c ( 2 m E ) ^ { 1 / 2 }$\\
(3) $\frac { 1 } { c } \left( \frac { E } { 2 m } \right) ^ { 1 / 2 }$\\
(4) $\left( \frac { E } { 2 m } \right) ^ { 1 / 2 }$