We present results from a detailed analysis of theoretical and observed light curves of classical Cepheid variables in the Galaxy and the Magellanic Clouds. Theoretical light curves of Cepheid variables are based on non-linear convective hydrodynamical pulsation models and the observational data are taken from the ongoing wide-field variability surveys. The variation in theoretical and observed light curve parameters as a function of period, wavelength and metallicity is used to constrain the input physics to the pulsation models, such as the mass-luminosity relations obeyed by Cepheid variables. We also account for the variation in the convective efficiency as input to the stellar pulsation models and its impact on the theoretical amplitudes and Period-Luminosity relations for Cepheid variables.