one question about refraction

The intensity of light after refraction, in fact, depends on the angle of incidence and the refractive index of the material.

Qualitatively, light is electromagentic waves which have two polarizations perpendicular to each other. On reflection at the surface of a medium, the two polarizations are not equally reflected with the same intensity (this is the reason why unpolarized light could become partially polarized on reflection).
Analysis with electromagentic theory could establish a relation between the light intensity on reflection with incident angle and refractive index of the reflecting material.

The energy of the reflected ray and that of the refracted ray add up together must equal to the energy of the incident ray (Law of Conservation of Energy, and assume negligible absorption by the medium). As a result, the intensity of the refracted light also varies with angle of incidence and refractive index.

An equation describing how reflected light intensity varies with incident angle and refractive index lis given in the following web-page:

http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=37

You could play with the animation and observe how the intensity of the reflected ray varies with incident angles. The theory and equation are given in the description below the animation.