Back to parabolas...
Remember the parabolas we saw before? In bridges... and paths of projectiles like when you throw a ball in the air.
They have cool reflective properties too.
Check it out:
|This is why paraboloids are used as satellite dishes and as the mirrors in telescopes.
And check out these flood lights:
Can you see from the reflective properties who paraboloids would make great flood lights? (Compare this to the ellipsoidal spot lights.)