When white light passes through a prism, it will refract and disperse into the seven colors of the visible spectrum - red, orange, yellow, green, indigo, blue, and violet. This is because white light is composed of a mixture of colored lights. To produce a rainbow, the sun light must hit water droplets inside a certain angle so that the light undergoes total internal reflection inside the droplets and is seen by the observer.

2.  You will have one Glass prism, screen and ray-
box
 Try to set your apparatus as you like
Questions
 what will you observe after your setting?
 If you are scientist, what hypothesis will you
suggest?

3.  When white light pass the prism, the light will
refract and disperse into seven colours.
 White light is a mixture of coloured lights.
 They are red, orange, yellow, green, indigo, blue
and violet.
 This is called colour spectrum.

4.  How to make rainbow by yourself?
http://hk.youtube.com/watch?v=fIbxHqPyF2U

5.  Why does the man stand against the sunlight when
he is making the rainbow?
 Answer: Only when the sun light from our backside
can produce totally internal reflection, and received
by ours eyes.

6.  Misconception
Rainbow is produced just by one droplet

7.  http://hk.youtube.com/watch?v=LoL1Mn5v6GY