ClipArt ETC
"Camera obscura strictly signifies a darkened chamber, because the room must be darkened, in order to observe its effects. To witness the phenomena of this instrument, let a room be closed in every direction, so as to exclude the light. Then from an aperture, say of an inch in diameter, admit a single beam of light, and the images of external things, such as trees and houses, and persons walking the streets, will be seen inverted on the wall opposite to where the light is admitted, or on a screen of white paper, placed before the aperture. The reason why the image is inverted will be obvious, when it is remembered that the rays proceeding from the extremities of the object must converge in order to pass through the small aperture; and as the rays of light always proceed in straight lines, they must cross each other at the point of admission. Thus the pencil a, coming from the upperpart of the tower, and proceeding straight, will represent the image of the part at b, while the lower part c, for the same reason, will be represented at d." —Comstock, 1850

Camera Obscura

"Camera obscura strictly signifies a darkened chamber, because the room must be darkened, in order to…

"Camera obscura strictly signifies a darkened chamber, because the room must be darkened, in order to observe its effects. To witness the phenomena of this instrument, let a room be closed in every direction, so as to exclude the light. Then from an aperture, say of an inch in diameter, admit a single beam of light, and the images of external things, such as trees and houses, and persons walking the streets, will be seen inverted on the wall opposite to where the light is admitted, or on a screen of white paper, placed before the aperture. The reason why the image is inverted will be obvious, when it is remembered that the rays proceeding from the extremities of the object must converge in order to pass through the small aperture; and as the rays of light always proceed in straight lines, they must cross each other at the point of admission. Thus the pencil a, coming from the upperpart of the tower, and proceeding straight, will represent the image of the part at b, while the lower part c, for the same reason, will be represented at d." —Comstock, 1850

Camera Obscura

"Camera obscura strictly signifies a darkened chamber, because the room must be darkened, in order to…

"Since A is producing light and larger than object B, the shadow of B continuously shrinks to a single point at C." —Quackenbos 1859

Diminish Shadow

"Since A is producing light and larger than object B, the shadow of B continuously shrinks to a single…

Hornblende is a complex inosilicate series of minerals. Hornblende is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole.

Hornblende

Hornblende is a complex inosilicate series of minerals. Hornblende is not a recognized mineral in its…

"The Knight, Death, and the Devil. By Albrecht Dürer. From the engraving on copper." -Heath, 1901

The Knight, Death, and the Devil

"The Knight, Death, and the Devil. By Albrecht Dürer. From the engraving on copper." -Heath, 1901

Principle of light and shade from light to dark.

Light and Shade

Principle of light and shade from light to dark.