Refracting Telescopes:
•A refracting telescope has two converging (convex) lenses of different POWERS set in line with each other. The lenses can be moved closer or further away from each other to focus the image. The smaller lens is called the EYEPIECE and the larger lens is called the OBJECTIVE LENS. The light gathering power of the telescope is given by D which is the DIAMETER of the lens. REMEMBER: when using angles, the angle of incidence always equals the angle of refraction!
Reflecting Telescopes:
•The reflecting telescope is made up of a large concave mirror to collect reflected light from a distant object like a planet in our solar system. The concave mirror also converges the light to a small plane mirror for the observers eye. The eye lens acts like a magnifying glass to increase the size of the virtual image. Reflecting telescopes have the advantage over refracting telescopes of having bigger mirrors without the image disorting.
Hubble's Telescopes:
The Hubble Telescope is in a fixed position outside the earth's atmosphere. The benefit of it being outside the earth's atmosphere is that the atmosphere absorbs and refracts some of the radiation given out by the stars; so placing a telescope outside the atmosphere ensures that all of the radiation emitted reaches the telescope thus giving a much clearer image.
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