1. What do we call the small wavelength that we can see?

Question

2. How does light travel?

3. What type of lenses are used in a refracting telescope?

Answer 1

1. The visible part of the spectrum runs from the shortest (violet) to the longest (red).
2. You may want to read about the dualistic nature of light; i.e., waves vs paricles.

3. You may be thinking of convex lenses.