can a sphere has a critial angle
I'm afraid you'll have to be a little more specific.
i mean why the water drop can total internal reflect and we can see a rainbow.I THINK CIRLCE DOES NOT HAS TOTAL REFLECT
The light is refracted twice. Once when it enters the drop of water, and a second time when it exits. The angle of refraction depends on the wavelenght of the light. So red will be refracted at a different angle than blue. The whole thing works like a prism, and you get your rainbow. Is that what you wanted to know?
Separate names with a comma.