A student has to trace the path of a ray of light passing through a rectangular glass slab for four different values of angle of incidence.(a) Write two important precautions for this experiment.(b) List two conclusions the student will draw based on his experiment.

 (a) Make sure the glass slab is:

1. Clean and free from air bubbles.

2. The pin should be fixed in verticle position and all pins should be placed in a straight line.

3. The glass slab should be perfectly rectangular with all its faces smooth.

(b) The two conclusions drawn by the student on his experiment are:

1. The incident ray, refracted ray, and normal all lie on the same plane.

2. The incident ray and the refracted ray are on the opposite sides of normal.

     $\frac {sin\ i}{sin\ r}=constant$