P1.1 -- The Solar System:
- Greek astronomer Ptolomy developed a geocentric model in which the Sun and the other plants revolved around the Earth.
- This was generally accepted until Copernicus suggested that Ptolomy's measurements actually better fit a heliocentric model in which the Earth and other planets revolved around the Sun. This however was quite controversial and was widely attacked, particularly by the Church.
- At the end of the 16th century the telescope was invented and using it Galileo discovered four of the moons orbiting Jupiter. This proved that not everything orbited the Earth and thus disproved the geocentric model, although on its own it did not necessarily prove the heliocentric model.
- Today, the light given out by luminous objects in space can be photographed at a far greater level of detail than drawings could provide, and other telescopes have been invented which can pick up non-visible energy-carrying waves such as radio waves and microwaves.
P1.2 -- Refracting telescopes:
- At an interface, or boundary, between two materials, a light wave can change direction. This is called refractions. When light moves from a material where it travels faster to one where it travels slower, it refracts towards the normal (a line perpendicular to the interface); if the opposite change occurs, it refracts away from the normal.
- A lens is a transparent which has been shaped in such a way that its interface changes the direction of parallel light waves. A converging or convex lens is one in which the block is curved at both ends, making it thicker at the middle.
- The focal length of a converging lens is the length between the lens and where the light rays are focused by the lens. This can be found by focusing an image of a distant object onto a screen, and measuring the distance between the lens and the screen.
- A refracting telescope uses two lenses; a convex lens to focus the light rays coming into the telescope onto a single point, thus forming an image, and an eyepiece lens to magnify the said image. The image formed is upside-down and small; after magnification it is enlargened but remains upside-down.
P1.3 -- Lenses (N/A: Practical):
P1.4 -- Reflecting telescopes:
- As well as being refracted, waves are also reflected at boundaries between materials. This means that when light passes through a lens, some light is reflected, which can make the image formed fainter.
- Refracting telescopes also must be very long to have large magnifications. Larger lenses can increase the magnification; however, they are very heavy and are difficult to make into a perfect shape. As well as this, the weight of the glass in the lens can cause the glass to begin to sag, which can affect the image produced. Reflecting telescopes, which use mirrors, avoid these problems.
- In a reflecting telescope, parallel light waves from a distant object are focused into a image by a primary mirror, which is then reflected by a secondary mirror onto a eyepiece lens, which magnifies the…
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