1. Stick two pins on the thermocol block in
parallel,
2. Place a source of light near to the thermocol
and observe the shadows. .
3. We can observe the shadows Diverging (moving away
from each other).
4. Now move the source and observe the angle of
divergence getting reduced.
5. As we goes on moving the source of light at a
long distance and at sufficient intensity, we observe Parallel rays are formed.