[3dem] lambda

[Ramanathan Natesh]

Hi All,

    Could anyone point me to a reference or show me how do we get from
classical formula for wavelength

lambda  = h/sqrt(2meV)    to   lambda = 12.398/sqrt[kV*(1022+kV)]

that is used in SPIDER glossary 
http://www.wadsworth.org/spider_doc/spider/docs/glossary.html#Lambda


m=mass 9.11 x 10^-31 Kg;  e=electron charge 1.6 x 10^-19 C 
h= 6.62 x 10^-34 J*sec V=voltage in volts
kV=kilo Volts.

    eg: for 120 kV  I get lambda = 0.03539 using classic formula but
                    I get lambda = 0.03349 from formula in SPIDER 
glossary.   Though the variation in 3rd decimal may/may not be 
significant.

thanks in advance,
natesh.