  Trace of ray deviated by a prism, which is common in a TIR (total internal
reflection) measurement system, is sometimes difficult to manage, especially if
the prism is an equilateral right angle prism (ERAP). The point where the ray
is reflected inside the right-angle prism is also changed as the angle of
incident ray changed. In an ATR (attenuated total reflectance) measurement
system, range of this point determines size of sample. Using JavaScript and
HTML5 model and visualization of ray tracing deviated by an ERAP is perform and
reported in this work. Some data are obtained from this visualization and an
empirical relations between angle of incident ray source \theta_S, angle of ray
detector hand \theta_D, and angle of ray detector \theta'_D are presented for
radial position of ray source R_S, radial position of ray detector R_D, height
of right-angle prism t, and refractive index of the prism n. Keywords:
deviation angle, equilateral right angle prism, total internal reflection,
JavaScript, HTML5.
