An illustration depicting an astigmatism. An optical system with astigmatism is one where rays that…

Diagram showing how to construct a conic when given the focus and the auxiliary circle. If the focus…

Diagram showing how to construct a conic when given the focus and the auxiliary circle. The focus is…

Diagram showing how to construct a conic when given the focus and the auxiliary circle. As the focus…

Illustration of half of an ellipse. "The ordinates of two corresponding points in an ellipse and its…

Illustration showing that if one diameter is conjugate to a second, the second is conjugate to the first.

Illustration of half of an ellipse and its auxiliary circle used to construct an ellipse by points,…

Diagram showing how to construct an ellipse when given the two foci and the length of the major axis…

Diagram of an ellipse that can used to illustrate the definition. "The constant ration between the distances…

Illustration showing the definition of an ellipse. "An ellipse is a curve which is the locus of a point…

Illustration of half of an ellipse. "If d denotes the abscissa of a point of an ellipse, r and r' its…

Diagram that illustrates "The algebraic sum of the distances of any point from the foci of a conic is…

Illustration of an ellipse with foci F' and F, major axis A' to A, minor axis B' to B, and center O.

Illustration of half of an ellipse. "If through a point P of an ellipse a line is drawn bisecting the…

Illustration of half of an ellipse. The square of the ordinate of a point in an ellipse is to the product…

Illustration showing that tangents drawn at the ends of any diameter are parallel to each other.

Diagram of an ellipse that can used to illustrate the different parts. Segment MN is the major axis,…

Illustration of half of an ellipse. "The sum of the distances of any point from the foci of an ellipse…

Illustration of how to draw a tangent to an ellipse from an external point.

Diagram an ellipse with a tangent line that illustrates "A line through a point on the ellipse and bisecting…

Illustration showing the tangents drawn at two corresponding points of an ellipse and its auxiliary…

"Diagram showing the Change in the Lens during Accomadation. On the right the lens is arranged for distant…

"A fire-place; a hearth; a brazier. The fire-place possessed a sacred character, and was dedicated among…

An illustration depicting the formation of circles of diffusion. "From point A luminous rays enter the…

"Heat is radiated at C, which is placed at mirror A's focus. Mirror A catches some of the heat and reflects…

Illustration of a hyperbola and its auxiliary circle. "Any ordinate of a hyperbola is to the tangent…

Diagram depicting a cone with both nappes intersected by plane J to form a hyperbola.

Illustration showing how the a hyperbola is symmetrical with respect to its conjugate axis.

Illustration showing how a hyperbola con be constructed by points, having been given the foci and the…

Diagram showing how to construct a hyperbola when given the two foci and the length of the major axis…

Illustration showing the definition of an hyperbola. "An hyperbola may be described by the continuous…

Illustration of a hyperbola with distances to foci drawn. "The difference of the distances of any point…

Illustration of a hyperbola with a line bisecting the focal radii. "If through a point P of an hyperbola…

Illustration of a point on a hyperbola. "If d denotes the abscissa (x-coordinate) of a point of an hyperbola,…

Illustration showing how to draw a tangent to an hyperbola from a given point P on the convex side of…

Diagram part of a hyperbola with a tangent line that illustrates "A line through a point on the hyperbola…

"A concave mirror reflects from a curved surface hollowing in like he inside of an orange." —Quackenbos…

"The focus of a concave mirror is the point where the rays are brought together by reflection." -Comstock…

"Parallel rays of light strike the concave mirror. The rays converge at the focus, F, which is halfway…

"...be made obvious...where the diverging rays 1, 2, 3, 4 form a focus at the point o, whereas, had…

"When the rays diverge from a point beyond the center of curvature, as B, the focus falls on the same…

"When the rays diverge form a point at a distance from the mirror less than that of the principal focus,…

"The focus of each point chose may be determined by tracing two rays from the point, and locating their…

"When the object is at a distance from the mirror somewhat greater than the center of curvature, as…

"...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…

"Suppose the tumbler, a, to be filled with water, and placed beyond the principal focus of the concave…

"A convex mirror reflects from a curved surface rounding out like the outside of an orange." —Quackenbos…

"Parallel rays strike the convex mirror, reflect, and diverge as if they had originated from a virtual…

The segments between the point of intersection of two tangents to a conic and their points of contact…

Diagram of a cone intersected by plane J to form a parabola. Also pictured is a circle formed by the…

Illustration showing the definition of a parabola as a conic section. "The section of a right circular…

Illustration showing the definition of a parabola as a conic section. "The section of a right circular…

Diagram showing how to construct a parabola when given the directrix (d), the focus (F) and the eccentricity…

Illustration of a parabola showing that any point of a parabola is the mean proportional between the…

Illustration of a parabola - a curve which is the locus of a point that moves in a plane so that its…