Ezzel a linkkel? http://www.fourmilab.ch/etexts/einstein/specrel/www/
Kattints már rá! lapozz le a végére.. És olvass!
Mi olyan nehéz ezen? idemásoljam?
"Thus, if we call the light energy enclosed by this surface E when it is measured in the stationary system, and ${\rm E}'$ when measured in the moving system, we obtain"