On the E-L equation and Snell’s law for massive particles : a mathematical revisit

D. N. Basu

Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata 700 064, India.

This article describes: (i) the conditions to check whether Euler-Lagrange equation for extremisation provides minimum or maximum and (ii) the derivation of Snell-Descartes law for massive particles which is in contradiction to that for the light waves.