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CAST — California Science Test Telescopes and Observing — practice questions

Explore 5 free Telescopes and Observing questions in CAST — California Science Test Science. Open each question or exercise to read its content, reference answers and available explanation.

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Telescopes and Observing questions and exercises with answers

Showing questions 1–5 of 5.

What are the two most important jobs a telescope does?Read the answer and worked solution →Why can a lens telescope not be built as large as a mirror telescope?Read the answer and worked solution →Each 10-meter Keck telescope reaches its full aperture using what arrangement?Read the answer and worked solution →A mirror 4 meters across gathers how much more light than one 1 meter across?Read the answer and worked solution →Observatories are put on high, dry, dark peaks. Which limitation does the dryness attack?Read the answer and worked solution →

Worked practice questions

What are the two most important jobs a telescope does?

  1. Magnify light and store it
  2. Collect light and focus it
  3. Split light and record it
  4. Warm light and steady it
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Correct answer: B. Collect light and focus it

1. Most objects astronomers study are far too faint for the eye alone. 2. A telescope first acts as a bucket that gathers the faint light. 3. It then brings all that light to a focus so it forms an image. 4. Magnifying is the job of the eyepiece, and recording is the job of the detector. _Source: OpenStax Astronomy (CC BY 4.0), section 6.1 Telescopes_

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Why can a lens telescope not be built as large as a mirror telescope?

  1. A big lens cannot be polished
  2. A big lens absorbs all light
  3. A big lens sags under its weight
  4. A big lens must sit outdoors
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Correct answer: C. A big lens sags under its weight

1. Light must pass right through a lens, so the lens can be held only at its rim. 2. Gravity then makes a large lens sag, which bends the light rays out of true. 3. The glass must also be flawless throughout and shaped precisely on both faces. 4. A mirror is supported from behind and only its front face must be shaped, so it can grow much larger. _Source: OpenStax Astronomy (CC BY 4.0), section 6.1 Telescopes_

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Each 10-meter Keck telescope reaches its full aperture using what arrangement?

  1. One thick glass mirror disc
  2. Two mirrors set end to end
  3. A ring of small lenses
  4. 36 hexagonal mirror pieces
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Correct answer: D. 36 hexagonal mirror pieces

1. A single 10-meter disc of glass would be far too heavy to hold in shape. 2. Each Keck telescope instead uses 36 hexagonal mirrors, each 1.8 meters wide. 3. Computer-controlled motors keep the 36 pieces aligned so they act as one surface. 4. The result collects light like a single mirror 10 meters across. _Source: OpenStax Astronomy (CC BY 4.0), section 6.2 Telescopes Today_

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