Reflectors, Cookers, and Other Phenomena
Watch this clip from 2:25 to the end.
Describe what you see here. Notice anything interesting?
Suppose a solar cooker has a parabolic cross section. Any object placed at the igniter will burn within seconds after the sun's rays start hitting the parabolic dish. 
Suppose we consider (0,0) = this parabola's vertex. 
Given this, 

- Find an equation for this parabola
 - Determine the depth of the dish.
 
Can skyscrapers melt cars and set surrounding buildings on fire? What do you think? If so, what causes this? Check this out.