CONIC SECTIONS: THE PARABOLAExamples from the Real World

Heater Heaters are sold which make use of the reflection property of the parabola. The heat source is at the focus and heat is concentrated in parallel rays. Have you walked by the parabolic reflector heater at COSTCO?

Satellite Dishes Satellite Dishes work on this same principle. Incoming waves are concentrated to the focus.

Automobile Headlights An automobile headlight is another example of a Paraboloid of Revolution -- taking a parabola and rotating it about its axis of symmetry. The smooth inner surface of the headlight is a glass reflector upon which bright aluminum has been deposited. This part is a powerful reflector. A parabolic reflector has the property that if a light source is placed at the focus of the reflector, the light rays will reflect from the mirror as rays parallel to the axis. This is used in auto headlights to give an intense concentrated beam of light.

For safer night driving, we do not want all the light rays to be parallel to the axis. Some light must be aimed far down the road, to the side, upward for signs or bridges.        So we offset the filament from the focus and change the beam entirely.         In most of today's cars, a 4 Lamp System is used -- 2 filament sealed beam units in 2 lamps.        The position of the filaments accomplishes most of the desired illumination patterns. The rest is taken care of by special lenses which contain prism  to bend the light rays.

McDonald's Arches McDonald's Arches are parabolas.

Path of a Ball Gallileo was the first to show that the path of an object thrown in space is a parabola.

Golden Gate Bridge The cables that act as suspension are parabolas.

Le Four Solaire at Font-Romeur There is a reflector in the Pyrenees Mountains that is 8 stories high. It cost two million dollars to build and it took ten years to build it. It is made of 9,000 mirrors arranged in a parabolic mirror. It can reach 6,000 degrees Fahrenheit just from the Sun!

Parabolic Receivers A person who whispers at the focus of one of the parabolic reflectors can be heard by a person located near the focus of the other parabola.

Fountains Bellagio's fountains at Las Vegas exhibit water in the shapes of parabolas.

Can you think of any parabolas that you may have seen?