Observing Space : Telescopes

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Human eyes can see visible light with wavelengths between 400 nm to 800 nm (nanometers). This is called visible radiation. Light waves with wavelengths outside this range are invisible to our eyes.

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1. Radio waves (longest, >20 cm) 2. Microwaves (0.3 mm - 20 cm) 3. Infrared waves (800 nm - 0.3 mm) 4. Visible light (400 nm - 800 nm) 5. Ultraviolet rays (300 pm - 400 nm) 6. X-rays (3 pm - 300 pm) 7…

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Hans Lippershey, a spectacle maker and researcher, discovered the first telescope in 1608. He found that looking through two lenses placed one behind the other makes objects appear closer. Galileo lat…

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Using his telescope, Galileo discovered: 1. Many more stars than visible to naked eyes 2. The moons of Jupiter 3. Black spots on the Sun 4. These observations revolutionized our understanding of space…

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A refracting telescope uses lenses to collect and focus light. It has: 1. Objective lens: Large lens that collects maximum light from space objects 2. Eyepiece: Smaller lens that produces magnified im…

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1. Large lenses are very difficult and expensive to make, and they become heavy and distorted 2. The telescope becomes very long and difficult to manage as lens size increases 3. Chromatic aberration …

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Reflecting telescopes use concave mirrors instead of lenses: 1. Large mirrors are easier to make than large lenses 2. Big mirrors can be made by combining smaller pieces 3. Mirrors are lighter than le…

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In a Newtonian telescope: 1. Light from space hits a large concave mirror 2. Reflected light rays are deflected by a small plane mirror before reaching focus 3. Light gets focused at a point perpendic…