Notice the figure 5.6 in the textbook of glass prism.

1. what is the reason for the incident ray of light in the fig to reflect in this way ?
2. if angle of incidence =30,what will happen to the light ray passing through the prism ?

2- 

Here, AB=Incident ray
angle of incidence, i=30 degree
BC=Refracted ray
CD=emergent ray
Angle of refraction, =r
Angle of emergence=e
Angle of deviation=$\delta$
Angle BMC=Prism angle=A
When light is incident at 30 degree, then after refraction the light ray bends towards the normal i.e. angle of refraction will be less than 30 degree.
Also there is a relation between the above angles.
$\mathrm{A}+\mathrm{\delta }=\mathrm{i}+\mathrm{e}$