"If light from a highly luminous body is admitted to a darkened room through a small hole in the shutter and ther received upon a white screen, it will form an inverted image of the object." -Avery 1895

Image by Aperature

"If light from a highly luminous body is admitted to a darkened room through a small hole in the shutter…

Component that is part of a larger construction

Building Block

Component that is part of a larger construction

An electric vacuum cleaner.

Electric Vacuum Cleaner

An electric vacuum cleaner.

"Showing how the image of an object which is seen is formed on the retina of the eye." —Croft 1917

Eye Focusing on Object

"Showing how the image of an object which is seen is formed on the retina of the eye." —Croft…

An illustration of a hand holding letters.

Hand Holding Letters

An illustration of a hand holding letters.

An illustration of a hand holding a military toy figurine.

Hand Holding Military Toy Figurine

An illustration of a hand holding a military toy figurine.

An illustration of a key.

Key

An illustration of a key.

An illustration of a man standing in the palm of a hand.

Man in Palm of Hand

An illustration of a man standing in the palm of a hand.

"Let a be the distance at which an object can be see distinctly, and b, the distance at which the same object is seen through the lens, and supose tthe distance of a from the eye, be twice that of b. Then because the object is at half the distance that it was before, it will appear twice as large...." -Comstock 1850

Single Microscope

"Let a be the distance at which an object can be see distinctly, and b, the distance at which the same…

"...if the object is placed more remote from the mirror than the principal focus, and between the focus and the centre of the sphere of which the reflector is a part, then the image will appear inverted on the contrary side of the centre, and farter from the mirror than the object; thus, if a lamp be placed obliquely before a concave mirror, its image will be seem inverted in the air, on the contrary side of a perpendicular line through the centre of the mirror." -Comstock 1850

Object Beyond the Focus in a Concave Mirror

"...if the object is placed more remote from the mirror than the principal focus, and between the focus…

"...let us suppose the object a, to be placed before the mirror, and nearer to it than the principal focus. Then the rays proceeding from the extremities of the object without interruption, would continue to diverge in the lines o and n, as seen behind the mirror' but by reflection they are made to diverge less than before, and consequently to make the angle under which the meet more obtuse at the eye b, than it would be if they continued onward to e, where they would have met without reflection. The result therefore, is to render the image h, upon the eye, as much larger than the object a, as the angle at the eye is more obtuse than the angle at e." -Comstock 1850

Object Within the Focus in a Concave Mirror

"...let us suppose the object a, to be placed before the mirror, and nearer to it than the principal…

"Hence the image of the object, when reflected from the convex mirror, appears smaller than the object itself." -Comstock 1850

Object Diminished in Convex Mirror

"Hence the image of the object, when reflected from the convex mirror, appears smaller than the object…

"Rays from an object showing the reproduction of an image in a convex mirror." -Avery 1895

Convex Mirror Reproducing an Image of an Arrow

"Rays from an object showing the reproduction of an image in a convex mirror." -Avery 1895

"The construction for the image produced by a plane mirror depends upon the fact that the image of the object may be located by locating the images of a number of well chosen points in the surface of the object." -Avery 1895

Object in Plane Mirror

"The construction for the image produced by a plane mirror depends upon the fact that the image of the…

"Let S be the position of the spectator; O and B the position of distant objects. The rays O R and B R which proceed from them, strike the surface of the water very obliquely, and the light which is reflected in the direction R S is sufficient to make a sensible impression upon the eye. But in regard to objects such as A placed near the spectator, they are not seen reflected, because the rays A R' which proceed from them strike the water with but little obliquity; and consequently, the part of their light which is reflected in the direction R' S, towards the spectator, is not sufficient to produce a sensible impression upon the eye." —Wells, 1857

Reflection

"Let S be the position of the spectator; O and B the position of distant objects. The rays O R and B…

"Here, of the rays S A, S B, and S C, only the ray S C meets the eye of the spectator D. The spot C, therefore, will appear luminous to the spectator D, but no other spot of the water A B C." —Wells, 1857

Reflection

"Here, of the rays S A, S B, and S C, only the ray S C meets the eye of the spectator D. The spot C,…

"Regular reflection results from the incidence of radiant energy upon a polished surface. When a beam of light falls upon a mirror, the greater part of it is reflected in a definite direction as is illustrated, and forms an image of the object from which it came. A perfect mirror would be invisible." -Avery 1895

Regular Reflection

"Regular reflection results from the incidence of radiant energy upon a polished surface. When a beam…

"Suppose a, to be a distinct object, from which pencils of rays flow from every point toward the object lens b. The image of a, in consequence of the refraction of the rays by the object lens, is inverted at c, which is the focus of the eyeglass d, and through which the image is then seen, still inverted." -Comstock 1850

Refracting Telescope

"Suppose a, to be a distinct object, from which pencils of rays flow from every point toward the object…

An illustration of a three triangles created with boats and a lighthouse. This is an example illustration used to fine the height of an object situated about the plane of observation, and its height above the plane.

Triangle with Lighthouse

An illustration of a three triangles created with boats and a lighthouse. This is an example illustration…

An illustration of an urn.

Urn

An illustration of an urn.