- Donnie Darko (Wikipedia)
Donnie Darko is a 2001 American science fiction psychological thriller film written and directed by Richard Kelly and produced by Flower Films. It stars Jake Gyllenhaal, Jena Malone, Maggie Gyllenhaal, Drew Barrymore, Mary McDonnell, Katharine Ross, Patrick Swayze, Noah Wyle, Stu Stone, Daveigh Chase, and James Duval. Set in October 1988, the film follows Donnie Darko, an emotionally troubled teenager who inadvertently escapes a bizarre accident by sleepwalking. He has visions of Frank, a mysterious figure in a rabbit costume who informs him that the world will end in 28 days, 6 hours, 42 minutes and 12 seconds.
- Focal length (Wikipedia)
The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system’s optical power. A positive focal length indicates that a system converges light, while a negative focal length indicates that the system diverges light. A system with a shorter focal length bends the rays more sharply, bringing them to a focus in a shorter distance or diverging them more quickly. For the special case of a thin lens in air, a positive focal length is the distance over which initially collimated (parallel) rays are brought to a focus, or alternatively a negative focal length indicates how far in front of the lens a point source must be located to form a collimated beam. For more general optical systems, the focal length has no intuitive meaning; it is simply the inverse of the system’s optical power.