Click the red region to change the light direction.
Click other region of light source can move the light pen to differ location( even inside the prism).

Click one of the corner of the prism to change the shape of prism.
Click inside the prism to change its location.

When tracing of the light will terminated when the ray intensity is less than  than 0.4%.
The relative intensity for each ray is shown at the boundary.
Intensity of red and green are used to represent two different polarization.
The yellow light (sum of red light and green light) represent equal intensity of two polarization waves.

At Brewster's angle, only one of the polarized light is refracted, and other one is totally reflected.
The index of refraction for the prism is 1.5

1. Total internal reflection
2. Change in light intensity
3. There might be small bugs, did you find out?

Light will travel with different speed at different media, which cause the reflection and refraction.

For reflection: the angle of incidence is equal to angle of reflection.
For refraction: the Snell's law govern the angle
折射時 則滿足折射定律:

index of refraction for media 1:  angle of incidence 
index of refraction for media 2:  angle of refraction 

Part of the energy is reflected and the rest propagate into new media.
The ratio depend on incident angle and index of refraction ( refracted angle )
EM (transverse) wave can have  two polarization (perpendicular to each other and )

The intensity is proportional to 
The intensity of electric field changed when reflection/refraction occurs,

where , 
So the intensity for the reflected light  is proportional to

Since the energy is conserved, so we can find out the  intensity of refraction light.

For normal incident, both  and equal to zero.
The coefficient are the same = 
For light emit from air (n=1.) into glass (n=1.5)
The electric field scale to  = (1.5-1)/(1.5+1)=0.2
So the intensity of the reflection scale to 0.2²=0.04 ( 4% of incident light)
So 96% light will enter the glass and only  4% of light were reflected.

This java applet use above equations to calculate the relative intensity of each ray.

Author：Fu-Kwun Hwang, Dept. of physics, National Taiwan Normal University