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Light, Mirrors and Telescopes. Rajesh Gupta University of California, San Diego. Mr. Smith’s Class. We see things because they reflect light into our eyes:. Homework. We hear things when they vibrate. If something vibrates with a very quickly we say it has a _____ pitch.
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Light, Mirrors and Telescopes Rajesh Gupta University of California, San Diego. Mr. Smith’s Class
We see things because they reflect light into our eyes: Homework
We hear things when they vibrate If something vibrates with a very quickly we say it has a _____ pitch. If something vibrates with a vibrates slowly we say it has a ____ pitch. Words – low, high
Drawing sounds… This sound wave has a _____ frequency: This sound wave has a ___ _frequency:
Waves can be slow or fast • Light travels VERY FAST – around 300,000 kilometres per second. At this speed it can go around the world 8 times in one second.
Small wave to see small things • But we can use big waves to see large things
The Universe is a VERY Big Place • 1,000,000,000,000 galaxies • 100,000,000,000 - 1,000,000,000,000 stars in a galaxy • About 100,000,000,000,000,000,000,000 kilometers • Light takes 13 billion years to travel
Laser We can use light • Light travels in straight lines:
Light reflects Reflected ray Incident ray Mirror
Using mirrors • Two examples: 2) A car headlight 1) A periscope
Clear vs. Diffuse Reflection • Smooth, shiny surfaces have a clear reflection: Rough, dull surfaces have a diffuse reflection. Diffuse reflection is when light is scattered in different directions
Concave Mirrors Where have you seen it?
Telescopes • Optical Telescopes use light to see things • Reflecting telescopes use mirrors • Refraction telescopes use lenses • Bigger telescopes collect more light • See more things, see farther • If you double the area of the mirror, you collect four times as much light • Radio Telescopes use radio waves to see things • Can observe at night, through clouds, rains • Larger waves, so telescopes can be bigger
Refractors (lens based) are hard to make very large Yerkes Observatory 40 Inch refractor (1897)
Observatories • 100 in. (2.5 m) Hooker, Mount Wilson. Largest 1917-1948. (photo: Mount Wilson) • 200 in. (5 m) Hale, • Mount Palomar. Largest 1948-1974. (photo: Alain Maury) • BTA-6 (6 m), Mount Pashtoukov. Largest 1974-1993. (photo: SAO-RAS) • Keck I & II (9.8 m), Mauna Kea. Largest 1993- • (photo: WM Keck Observatory)
Observatories • Most are made in high locations and dry areas • Kitt Peak (Arizona), Mauna Kea (Hawaii), Andes Mnts (Chile)
Kitt Peak Observatories 24 Telescopes
CTIO (Chile) above Siding Springs (Australia) right
The Keck Telescopes Each is 10 meters across
The Very Large Telescope (VLT) 4 telescopes each with 8 m mirrors - acts like a 16 m telescope
The Overwhelmingly Large Telescope - OWL 100 meters across Is there no limit?!?!?!?!?
Radio Telescopes - Use same design as visible light telescope - a parabolic surface
Arecibo Radio Telescope Largest Single Dish 305 m across
The Very Large Array 27 Radio telescopes acting as one Radio Image of a Supernova remnant
Space Telescopes X-Ray Chandra Telescope Infrared Spitzer Space Telescope Visible - Ultraviolet Hubble Space Telescope