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Light, Mirrors and Telescopes
Rajesh GuptaUniversity of California, San Diego.
Mr. Smith’s Class
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We see things because they reflect light into our eyes:
Homework
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We hear things when they We hear things when they vibratevibrate
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
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How do we see things?
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Indoors and outdoors
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We make or see or hear waves
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Drawing sounds…Drawing sounds…
This sound wave has a _____ frequency:
This sound wave has a ___ _frequency:
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Waves can be small or large
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Light travels VERY FAST – around 300,000 kilometres per second.
At this speed it can go around the world 8 times in one second.
Waves can be slow or fast
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Small wave to see small things
But we can use big waves to see large things
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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
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We can use different waves to see the universe
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We can use different waves to see the universe
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We can use different waves to see the universe
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We can use different waves to see the universe
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We can use different waves to see the universe
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We can use lightWe can use light
Light travels in straight lines:
Laser
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Light reflects Light reflects
Incident ray Reflected ray
Mirror
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Using mirrorsUsing mirrorsTwo examples:
1) A periscope
2) A car headlight
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Clear vs. Diffuse ReflectionClear 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
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Mirrors can be concave or convex
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Convex Mirrors
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Concave Mirrors
Where have you seen it?
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Concave Mirrors and Far Objects
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Refraction is bending of Refraction is bending of lightlight
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Lenses use refraction to form images
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Telescopes and Microscopes
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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
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Refractors (lens based) are hard to make very large
Yerkes Observatory
40 Inch refractor (1897)
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Reflecting Telescopes
• 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
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Observatories
Most are made in high locations and dry areas Kitt Peak (Arizona),
Mauna Kea (Hawaii), Andes Mnts (Chile)
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Kitt Peak Observatories
24 Telescopes
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CTIO (Chile) above
Siding Springs (Australia) right
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Mauna Kea Observatories - 12 telescopes of various sizes
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The Keck Telescopes
Each is 10 meters across
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Subaru Telescope - 8.3 meters
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The Very Large Telescope
(VLT)
4 telescopes each with 8 m mirrors - acts like a 16 m telescope
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The Overwhelmingly Large Telescope - OWL100 meters across
Is there no limit?!?!?!?!?
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Using Other Waves
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Radio Telescopes - Use same design as visible light telescope - a parabolic surface
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Arecibo Radio Telescope
Largest Single Dish
305 m across
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Radio Telescope: Arcibo, Puerto Rico
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The Very Large Array
27 Radio telescopes acting as one
Radio Image of a Supernova remnant
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Radio Telescopes: Green Bank, West Virginia
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Ooty Radio Telescope
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GMRT: Giant Metrewave
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Space Telescopes
InfraredSpitzer Space Telescope
Visible - UltravioletHubble Space Telescope
X-RayChandra Telescope
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Hubble Space Telescope
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Acknowledgements Material collected from diverse and many sources, including
http://observe.phy.sfasu.edu/courses/phy410/lectures410/Movies/sound/ http://science.howstuffworks.com/light14.htm http://www.kidskonnect.com/LightSound/LightSoundHome.html The Soundry: How We Perceive Sound: The Ear The Science Spot: Physics - Light & Sound What are waves?, NASA Physics Zone: Lessons on Waves, Light, and Sound http://www2.biglobe.ne.jp/~norimari/science/JavaEd/e-wave6.html Waves, Light and Sound Review
http://www.glenbrook.k12.il.us/gbssci/phys/reviews/63reviews/u11and12/u1112rev.html http://online.physics.uiuc.edu/courses/phys150/fall03/slides/lect11.pdf P100_Class10_ICQ.pdf (application/pdf Object) http://www.astro.ubc.ca/people/newbury/astro311/notes/060925h.pdf Waves&Superposition.pdf (application/pdf Object) http://www.ifa.hawaii.edu/~stalder/astro110/lectures/lecture9.pdf http://www.colloid.nl/Education/Nat1chem/waves-lectures-Nat-Chem-2006.pdf The educational encyclopedia, physics, optics and color The Physics Classroom http://faculty.salisbury.edu/~jwhoward/astro108/html/present.htm Giant Meterwave Radio Telescope; Ooty Radio Telescope http://www.ece.vt.edu/swe/RFI2004/35.pdf