# Conic projection of a sphere

Chandi
Hi everybody,

Guys I'm a total stranger to physics. I need some help to find the relationship between the major/minor axes of an ellipse and the radius of a sphere in a cone of light.

For example, imagine a light source is located at 'h' height from a plane and a sphere(with a radius of 'r') is located at y vertical distance from the source of light and horizontally deviated at x distance from the perpendicular axis of the plane and the source of light.
Obviously if the horizontal deviation is zero, then the projection is a circle. But I would like to know the relationship of the ellipse to the radius of the sphere when horizontal deviation is not zero.

AC130Nav
Hi everybody,

Guys I'm a total stranger to physics. I need some help to find the relationship between the major/minor axes of an ellipse and the radius of a sphere in a cone of light.

For example, imagine a light source is located at 'h' height from a plane and a sphere(with a radius of 'r') is located at y vertical distance from the source of light and horizontally deviated at x distance from the perpendicular axis of the plane and the source of light.
Obviously if the horizontal deviation is zero, then the projection is a circle. But I would like to know the relationship of the ellipse to the radius of the sphere when horizontal deviation is not zero.

First thing comes to mind is chart conic projections (search for <cartography AND "conic projection"> or <"Lambert Conformal">.

But that doesn't explain the reference to an elipse. Possibly you are referring to perspective as used in drawings.

Also, you mentioned not having a background in physics, but how's your math?