  We calculate the density distribution of protons and neutrons for $^{40,42,
44,48}Ca$ in the frame-work of relativistic mean field (RMF) theory with NL3
and G2 parameter sets. The microscopic proton-nucleus optical potential for
$p+^{40}Ca$ system is evaluted from Dirac NN-scattering amplitude and the
density of the target nucleus using Relativistic-Love-Franey and
McNeil-Ray-Wallace parametrizations. Then we estimate the scattering
observables, such as elastic differential scattering cross-section, analysing
power and the spin observables with relativistic impulse approximation. We
compare the results with the experimental data for some selective cases and
found that the use of density as well as the scattering matrix parametrization
is crucial for the theoretical prediction.
