Light, Mirrors and Telescopes Rajesh Gupta University of California, San Diego. Mr. Smith’s Class

2 We see things because they reflect light into our eyes: Homework

3 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

4 How do we see things?

5 Indoors and outdoors

6 We make or see or hear waves

7 Drawing sounds… This sound wave has a _____ frequency: This sound wave has a ___ _frequency:

8 Waves can be small or large

9 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

10 Small wave to see small things  But we can use big waves to see large things

11 The Universe is a VERY Big Place  1,000,000,000,000 galaxies  100,000,000, ,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

12 We can use different waves to see the universe

13 We can use different waves to see the universe

14 We can use different waves to see the universe

15 We can use different waves to see the universe

16 We can use different waves to see the universe

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18 We can use light Light travels in straight lines: Laser

19 Light reflects Incident ray Reflected ray Mirror

20 Using mirrors Two examples: 1) A periscope 2) A car headlight

21 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

22 Mirrors can be concave or convex

23 Convex Mirrors

24 Concave Mirrors Where have you seen it?

25 Concave Mirrors and Far Objects

26 Refraction is bending of light

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28 Lenses use refraction to form images

29 Telescopes and Microscopes

30 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

31 Refractors (lens based) are hard to make very large Yerkes Observatory 40 Inch refractor (1897)

32 Reflecting Telescopes

100 in. (2.5 m) Hooker, Mount Wilson. Largest (photo: Mount Wilson) 200 in. (5 m) Hale, Mount Palomar. Largest (photo: Alain Maury) BTA-6 (6 m), Mount Pashtoukov. Largest (photo: SAO-RAS) Keck I & II (9.8 m), Mauna Kea. Largest (photo: WM Keck Observatory) Observatories

34 Observatories  Most are made in high locations and dry areas Kitt Peak (Arizona), Mauna Kea (Hawaii), Andes Mnts (Chile)

35 Kitt Peak Observatories 24 Telescopes

36 CTIO (Chile) above Siding Springs (Australia) right

37 Mauna Kea Observatories - 12 telescopes of various sizes

38 The Keck Telescopes Each is 10 meters across

39 Subaru Telescope meters

40 The Very Large Telescope (VLT) 4 telescopes each with 8 m mirrors - acts like a 16 m telescope

41 The OverwhelminglyOverwhelmingly Large TelescopeLarge Telescope - OWL 100 meters across Is there no limit?!?!?!?!?

42 Using Other Waves

43 Radio Telescopes - Use same design as visible light telescope - a parabolic surface

44 Arecibo Radio Telescope Largest Single Dish 305 m across

45 Radio Telescope: Arcibo, Puerto Rico

46 The Very Large Array 27 Radio telescopes acting as one Radio Image of a Supernova remnant

47 Radio Telescopes: Green Bank, West Virginia

48 Ooty Radio Telescope

49 GMRT: Giant Metrewave

50 Space Telescopes Infrared Spitzer Space Telescope Visible - Ultraviolet Hubble Space Telescope X-Ray Chandra Telescope

51 Hubble Space Telescope

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53 Acknowledgements  Material collected from diverse and many sources, including The Soundry: How We Perceive Sound: The Ear The Science Spot: Physics - Light & Sound What are waves?, NASA What are waves? Physics Zone: Lessons on Waves, Light, and Sound Waves, Light and Sound Review  P100_Class10_ICQ.pdf (application/pdf Object) Waves&Superposition.pdf (application/pdf Object) The educational encyclopedia, physics, optics and color The Physics Classroom Giant Meterwave Radio Telescope; Ooty Radio Telescope Giant Meterwave Radio TelescopeOoty Radio Telescope