The Atmosphere The sky is blue because blue light from the Sun is scattered more than bigger wavelengths so appears to come from all directions Most of the atmosphere is Nitrogen. The 21% oxygen and water vapour it contains is important for human survival. Visible light, microwaves and some radio waves can pass through the atmosphere Infra red, ultra violet and x rays are mostly absorbed so observatories tend to be high up or in space. The light from stars is slightly distorted as it refracts through different layers in the Earth’s atmosphere, especially if pollution is present. Light pollution may be caused by light from human activity. If the background sky is less dark the stars stand out less and so are harder to see. Telescopes A refracting telescope uses lenses to produce a magnified image A reflecting telescope includes a large mirror to produce a magnified image It is much easier and cheaper to produce a... [continues]
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