Light and Telescopes

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Light and Telescopes
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A Telescope is a tool used to gather light from
objects in the universe
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There are two different types of telescopes

• A refracting telescope uses a glass lens to
  concentrate incoming light
• A reflecting telescope uses mirrors to
  concentrate incoming starlight

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Three main functions of a telescope

• Most important!!
• Gather More Light (bigger better) making
  objects appear brighter
• followed by
• to see fine detail
• (called resolution)
• and least important,
• magnify
• magnification (objective lens focal length /
  eyepiece lens focal length)

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A larger objective (lens or mirror) provides a
brighter (not bigger) image
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If you pass white light through a prism, it
separates into its component colors.
long wavelengths
ROY G B I V
short wavelengths
spectrum
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But visible light is only one type of
electromagnetic radiation (light) emitted by stars
Astronomers are interested in the entire spectrum
of Light!
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Consider This Class as Seen in Different
Wavelengths of Light!
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Consider Orion as Seen in Different Wavelengths
of Light!
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Observations at other wavelengths are revealing
previously invisible sights
UV
infrared
Map of Orion region
Ordinary visible
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Hubble Space Telescope Views of Orion Nebula
showing stars hidden in clouds http//oposite.stsc
i.edu/pubinfo/pr/97/13/A.html
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Sun as seen in visible light from Earth and from
space in X-rays by satellites
http//solar.physics.montana.edu/tslater/real-time
/
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Radio telescopes
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The Very Large Array (VLA) in New Mexico
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Twinkle, twinkle, little star
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Atmospheric seeing
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• How can we improve the image quality?
• Bigger telescope mirror
• Location, location location! (mountain tops,
  space)
• Adaptive optics

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The planet Uranus imaged in the infrared
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Earths atmosphere refracts light images are
blurry!
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• The Hubble Space Telescope is in space for 2
  reasons
• refraction (bending of optical starlight)
• absorption (of near ultraviolet and infrared)

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visible
Near infrared
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Some EM radiation is absorbed by Earths
atmosphere.
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Tutorial Telescopes and Earths Atmosphere pg.
43

• Work with a partner!
• Read the instructions and questions carefully.
• Discuss the concepts and your answers with one
  another. Take time to understand it now!!!!
• Come to a consensus answer you both agree on.
• If you get stuck or are not sure of your answer,
  ask another group.

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Which is the correct reasoning for why a gamma
ray telescope located in Antarctica that is to be
used to look for evidence of black holes in the
centers of galaxies would not get funded?

1. There is no way to detect the presence of a black
   hole.
2. Gamma rays are too energetic to detect with a
   telescope.
3. You cant build a functioning telescope in
   Antarctica.
4. Gamma rays dont penetrate Earths atmosphere.

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Imagine youre the head of a funding agency that
can afford to build only one telescope. Which of
the three proposed telescopes below would be best
to support?

1. A gamma ray telescope in Antarctica
2. A radio telescope in orbit above the Earth
3. A visible telescope located high on a mountain in
   Peru
4. An ultraviolet telescope located in the Mojave
   desert

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Imagine that you throw a ball directly upward.
Which of the following statements best describes
how Newtons second law accounts for the motion
of the ball when it reaches its maximum height?

1. The ball has a velocity that is zero and an
   acceleration that is zero.
2. The ball has a velocity that is upward and an
   acceleration that is downward.
3. The ball has a net force that is downward and a
   velocity that is downward.
4. The ball has a net force that is downward and an
   acceleration of zero.
5. The ball has a net force that is downward and an
   acceleration that is downward.