Shadow
From Free net encyclopedia
- This article is about the optical phenomenon; for other meanings, see Shadow (disambiguation).
A shadow is a region of darkness where light is blocked. A shadow occupies all the space behind an opaque object with light in front of it. The cross-section of a shadow is a two-dimensional silhouette, or reverse projection of the object blocking the light.
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Features
Image:Staxringold Coolshot 1.jpg Image:Poged sa tornja na senku.JPG The smaller the angle between an elongated object and the direction of the light it blocks, the shorter its shadow. The smaller the angle between the direction of the light and the surface on which the shadow occurs, the longer the shadow is. If the object is close to the light source, the shadow is large. If the surface is curved there are further distortions.
For non-point sources of light, the shadow is divided into the umbra and penumbra. The wider the light source, the more blurred the shadow.
If there are multiple light sources there are multiple shadows, with overlapping parts darker, or a combination of colors. For a person or object touching the surface, like a person standing on the ground, or a pole in the ground, these converge at the point of touch.
Colored shadows
If white light is produced by separate colored light sources, the shadows are colored.
Illuminate a room with a red light, and the shadows are exclusively gray, or dark. Illuminate the shadows with a white light, and the shadows are green. Where both lights are blocked, or in other words where the shadows intersect, the shadows are gray. Away from the intersection, where the red light is blocked the shadows are green, and where the white light is blocked the shadows are red. In other words, light colors shadows or brightens them, according to the complementary color of the light blocked to cast the shadow. In the case of white and red lights, the complement of white is red; with white and green lights, the complement of white is green.
In the absence of multiple light sources, colored lights illuminate spaces where other lights are not blocked. In the above example, the red shadow cast by blocking white light is not a shadow with the white light off, but it is illuminated in red.
In the absence of white light, colored lights blocked by an opaque surface cast shadows in the colors complementary to the lights blocked. For green light, red shadows, and vice-versa; blue, orange; yellow, purple; intermediate light, intermediate shadows.
Image:British Library Gate Shadow.jpg
Other notes
A shadow cast by the Earth on the Moon is a lunar eclipse. Conversely, a shadow cast by the Moon on the Earth is a solar eclipse.
On satellite imagery and aerial photographs, taken vertically, tall buildings can be recognized as such by their long shadows (if the photographs are not taken in the tropics around noon) , while these also show more of the shape of these buildings.
A shadow shows, apart from distortion, the same image as the silhouette when looking at the object from the sun-side, hence the mirror image of the silhouette seen from the other side (see picture).
The term shadow is also used with regard to other things than light, for example rain: a rain shadow is a dry area, which, with respect to the prevailing wind direction, is beyond a mountain range; it is dry because air masses lose part of their water when they move over these mountains.
Furthermore, it is possible to see shadows by moonlight on clear evenings.
Fiction
- In Peter Pan the main character loses his shadow: it snaps off when he leaps out of the window, which is slammed closed behind him. It is put in a drawer and later sewed back on by Wendy.
- In many fantasy games, shadow is widely referred to as the source of dark arts and black magic. Shadows, mainly in this genre, are said to be the departed souls of people that have had their lives tragically cut short or did not receive acceptance in heaven or hell.
- In Roger Zelazny's novel Jack of Shadows, the main character has a unique ability to manipulate shadows magically.
- In the Chronicles of Amber series of novels (also by Zelazny), Shadow is a metaphysical substance in which all possible universes can exist, if a person who meets certain criteria desires to go to them.
- In Final Fantasy Tactics Advance, Assassins can bind a target's shadow to the ground, paralyzing them in time and space.
- In The Lord of the Rings by J.R.R. Tolkien, Mordor is the land 'where shadows lie.'
- Victoria by Knut Hamsun and Hard-Boiled Wonderland and the End of the World by Haruki Murakami feature a character depriving people of their shadows when approaching the end of the world.
- In ninja fiction, ninjas are supposedly able to become "one with the shadows" or, "a living shadow." In the manga Naruto, a special shuriken is named "The Windmill of Shadows." Also, in the game Samurai Warriors, Hanzo Hattori Can reach a level named the shadow.
- In Slayers and an episode of Inuyasha, throwing a knife onto the ground in a person's shadow would paralyze them, aptly named "Shadow Bind".
- In DC Comics, both Obsidian and Shadow-Thief have abilities over shadow.
Heraldry
In heraldry, when a charge is supposedly shown in shadow (the appearance is of the charge merely being outlined in a neutral tint rather than being of one or more tinctures different from the field on which it is placed), it is called umbrated. Supposedly only a limited number of specific charges can be so depicted.
See also
es:Sombra fr:Ombre (lumière) he:צל nl:schaduw nn:Skugge ja:影 pl:Cień fizyczny pt:Sombra ru:Тень