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Physics
Classical Physics
Optics
May I treat the light from a star as a light beam?
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[QUOTE="Drakkith, post: 6833469, member: 272035"] To elaborate, when talking about the 'shape' of the incoming light we can do a few things. First, we need to decide if we're talking about light from a single point or light from a region of interest (like all the light from the surface of a star). For light coming from a single point we usually treat it as an expanding cone whose base is the diameter of the aperture of the optical system and whose point starts are the point of emission/reflection. When the distance to the target is so large that the cone's side angles are extremely close to 90 degrees we often just treat the light as a 'beam' instead of a cone and say that all the rays are parallel to each other. For light from a region of interest, we have a different shape. Instead of a pointed cone, we have a cone with its top 'chopped off'. The base is the diameter of the target region and the 'top' is the diameter of the aperture of the optical system. All the light cones from each point that reach the optical system are contained within the shape. For objects like stars that are at extreme distances and also have extremely small angular diameters, we can treat the light from both individual points and from the entire region as if it comes from a point source. That is, the light rays from any single point on the target can be treated as if they parallel to each other and parallel to light rays from other points on the target. As for how wave optics treats point-like sources, I can't say much. I was under the impression that you treat the whole thing as a single wave front coming from a single point. [/QUOTE]
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Physics
Classical Physics
Optics
May I treat the light from a star as a light beam?
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