Changing the shape of a parabola

Explore how the shape of the parabola is affected by the relationship between the focus and the directrix. You can drag any of the A, B, C points. Use this to answer the questions below.
1. Make a conjecture regarding what relatiosnhip between the focus and the directrix of a parabolla makes the parabolla look a) narrow; b) wide open. 2. Use the applet to explore your conjecture. 3. What happens to the parabolla if the focus lies on the directrix?