ASTR 101 Lecture Notes - Lecture 13: Charge-Coupled Device, Chromatic Aberration, Infrared Telescope
26 Dec 2017
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Document Summary
Telescopes use lenses to concentrate light - telescopes concentrate light but modern telescopes don"t use lenses - they use mirrors! Light bends towards the normal when it enters more optically dense material. This is because the speed of light is slower in that material than in the air/space that the light came from. Wavefronts generated at the surface of the material propagate slower, so the common wavefront is at an angle relative to the original source. Convex lenses bend light towards the optical axis. The fatter the lens, the more it bends light. This acts to concentrate the light; the light from a distant object is concentrated down to a point so dimmer objects are more visible. Although the moon is physically smaller as an image through a telescope, it appears larger due to concentration of light. The thicker the lens, the bigger the issue. Phone cameras have more chromatic aberration than large lenses.
