Illustration of a square inscribed in a closed concave geometric figure with 24 sides in the shape of…

Illustration of an equilateral triangle inscribed in a closed concave geometric figure with 24 sides…

"b is a glass tube in water and c is a glass tube in mercury. The surface of the water in the tube b…

"The contours of a concave (hollowed out) cone are close together at the center (top), and far apart…

"...and the cornea will become too flat, or not suffciently convex, to make the rays of light meet at…

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

Illustration of an irregular hexagon. This is also an example of a concave polygon.

Illustration of an irregular hexagon. This is also an example of a concave polygon with symmetry.

Illustration of an irregular hexagon. This is also an example of a concave polygon with symmetry.

Illustration of an irregular hexagon. This is also an example of a concave polygon with symmetry.

"A lens is a transparent body the two refracting surfaces of which are curved, or one of which is curved…

"The foci of concave mirrors may be in front of the mirror, in which case they are real; or they may…

"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…

"Thus, were the rays falling on the mirror parallel, the focus would be at a' but in consequence of…

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

"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…

"When the concave mirror is large, say six inches in diameter, and eight or ten inches focal distance,…

"...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 a red hot ball to be placed in the principle focus of the mirror, a, the rays of heat and light…

"The spherical aberration of a concave mirror is the deviation of some of the reflected light from the…

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

"Concave or Adherent Surface of the Nail. *A*, border of the root; *B*, whitish portion…

Illustration of a nonregular/irregular convcave nonagon. A nonagon is a closed geometric figure with…

Illustration of a nonregular/irregular convcave nonagon. A nonagon is a closed geometric figure with…

Illustration of a nonregular/irregular convcave nonagon. A nonagon is a closed geometric figure with…

Illustration of 2 regular congruent nonagons that have the same center. One nonagon has been rotated…

Illustration of an irregular concave octagon. This polygon has some symmetry.

Illustration of an irregular concave octagon. This polygon has some symmetry.

Illustration of an irregular concave octagon. This polygon has some symmetry.

Illustration of an irregular pentagon. This is also an example of a concave polygon with symmetry.

Illustration of a concave polygon. A concave polygon is a polygon of which tow or more sides, if produced,…

"If a pair of concave mirrors be set facing each other, as shown in figure 7, and a source of heat be…

"Hold a lamp reflector or other large concave mirror directly facing the sun, so as to bring the rays…

Illustration of a closed concave geometric figure with 20 sides in the shape of a 10-point star.

Illustration of a closed concave geometric figure with 24 sides in the shape of a 12-point star.

Illustration of a closed concave geometric figure with 16 sides in the shape of a 8-point star.

Illustration of a closed concave geometric figure with 18 sides in the shape of a 9-point star.