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The principal ray or chief ray (sometimes known as the b ray) in an optical system is the meridional ray that starts at an edge of an object and passes through the center of the aperture stop. [ 5 ] [ 8 ] [ 7 ] The distance between the chief ray (or an extension of it for a virtual image) and the optical axis at an image location defines the ...
A light ray is a line or curve that is perpendicular to the light's wavefronts (and is therefore collinear with the wave vector). A slightly more rigorous definition of a light ray follows from Fermat's principle, which states that the path taken between two points by a ray of light is the path that can be traversed in the least time. [1]
A ray with a terminus at A, with two points B and C on the right. Given a line and any point A on it, we may consider A as decomposing this line into two parts. Each such part is called a ray and the point A is called its initial point. It is also known as half-line, a one-dimensional half-space. The point A is considered to be a member of the ray.
If the space is two-dimensional, then a half-space is called a half-plane (open or closed). [2] [3] A half-space in a one-dimensional space is called a half-line [4] or ray. More generally, a half-space is either of the two parts into which a hyperplane divides an n-dimensional space. [2]
Coordinate x B and the horizontal coordinate p 1C of momentum p C completely define ray r C as it crosses axis x 1. This ray may then be defined by a point r C =(x B,p 1C) in space x 1 p 1 as shown at the bottom of the figure. Space x 1 p 1 is called phase space and different light rays may be represented by different points in this space.
Fig. 1: Fermat's principle in the case of refraction of light at a flat surface between (say) air and water. Given an object-point A in the air, and an observation point B in the water, the refraction point P is that which minimizes the time taken by the light to travel the path APB.
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The proof of the property on midpoints is best done for the hyperbola = /. Because any hyperbola is an affine image of the hyperbola y = 1 / x {\displaystyle y=1/x} (see section below) and an affine transformation preserves parallelism and midpoints of line segments, the property is true for all hyperbolas: