Light, Mirrors and Telescopes

Rajesh GuptaUniversity 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 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

4

How do we see things?

5

Indoors and outdoors

6

We make or see or hear waves

7

Drawing sounds…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 - 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

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

17

18

We can use lightWe can use light

Light travels in straight lines:

Laser

19

Light reflects Light reflects

Incident ray Reflected ray

Mirror

20

Using mirrorsUsing mirrorsTwo examples:

1) A periscope

2) A car headlight

21

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

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 Refraction is bending of lightlight

27

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 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

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 - 8.3 meters

40

The Very Large Telescope

(VLT)

4 telescopes each with 8 m mirrors - acts like a 16 m telescope

41

The Overwhelmingly Large Telescope - OWL100 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

InfraredSpitzer Space Telescope

Visible - UltravioletHubble Space Telescope

X-RayChandra Telescope

51

Hubble Space Telescope

52

53

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