Astronomy 101 – Test 3 Review, Fall 2015
This test will be in two parts, 100 points total.
Part 1: 20 questions worth 60 points, normal test covering Sections 3.5 – 4.3.
Part 2: 20 questions worth 40 points, General Education Assessment covering moon phases (Sec
2.3, see Test 2 review sheet) and light (Sec 4.1, parts of 4.2 and 4.3)
Online: Old Test 3 (and Old Test 2 #1-5 to review moon phases)
Chapter 3
Section 3.5
Know: satellite, orbit, unbound orbit, circular velocity, centripetal force
Answer:
Why do astronauts float?
If an object is orbiting at a constant speed, is it accelerating?
How is speed related to the shape of an orbit?
How do bound and unbound orbits differ?
Chapter 4
Section 4.1
Know: light, lightspeed, electromagnetic wave, transverse wave, wavelength, amplitude,
frequency, photon, EM spectrum
Answer:
What kind of a wave is light?
How is the wavelength of light related to its frequency? Its color?
How is wavelength and frequency related to speed of light?
How is the energy of a photon related to frequency and wavelength?
What causes electromagnetic waves?
What are the different types of light in order of increasing wavelength?
Section 4.2
Know: resolution, integration time, quantum efficiency, CCD, false-color, spectrometer,
diffraction grating
Answer:
How is the eye like a telescope?
What are some limitations of the eye?
What are some limitations to astronomy with a non-digital camera?
How does a CCD work?
What do filters do?
What are spectrometers used for?
How are the wavelength (or color), energy, and temperature of light related?
For example, light with a short wavelength (like blue) would have high energy
and indicate high temperatures
Section 4.3
Words to Know: Refractor, Reflector, Aperture, Focal length, Interferometer, Diffraction, seeing,
adaptive optics
Be able to Answer:
How do refractors and reflectors work? Where are lenses/mirrors?
How is focal length related to the size of an image?
What are some limitations of refractors?
What are some advantages of reflectors?
How are radio telescopes different from optical telescopes?
What do interferometers do?
What are some ways to observe wavelengths blocked by the atmosphere?
How is resolution related to the focal length of a telescope?
What are some limits to resolution?
How is diffraction related to the size of a telescope?
What causes stars to twinkle?
What are some ways to reduce the effects of astronomical seeing?
What wavelengths of light are blocked by the atmosphere?
Where is the best place to put a UV/IR/radio telescope (like lecture-tutorial)?
Clicker Questions:
Chapter 3
1) The Space Shuttle is in a circular orbit at a constant speed of 28,000 km/hr. Is gravity acting
on the spacecraft?
A. The spacecraft is not accelerating since the speed is constant. No force = no gravity.
B. The direction of the motion is constantly changing. This counts as an acceleration.
Forces produce gravity.
C. The astronauts inside are weightless. No weight equals no gravity.
Answer: B
Explanation: Choice A is incorrect because the velocity is composed of the speed and the
direction. Even if the speed is constant, the direction is changing (option B). Option C is incorrect
because gravity acts throughout space. The force is smaller if the separation is larger, but gravity
does not ever just stop.
Chapter 4
1. On the FM dial, the frequencies run from 88 to 107 MHz (million cycles per second). On the
AM dial, the range is 570 to 1600 kHz (thousand cycles per second).
Which statement(s) are true?
A. FM photons have shorter wavelengths than AM.
B. FM photons have higher energies than AM.
C. FM photons travel at the same speed as AM.
D. All the above statements are true.
Answer: D
Explanation: Light in the FM radio band has a higher frequency than AM, so it will have shorter
wavelengths and higher energies. All light travels at the same speed, regardless of its frequency.
2. Which of the following would be true about comparing gamma rays and radio waves?
a) The radio waves would have a lower energy and would travel slower than gamma rays.
b) The gamma rays would have a shorter wavelength and a lower energy than radio waves.
c) The radio waves would have a longer wavelength and travel the same speed as gamma
rays.
d) The gamma rays would have a higher energy and would travel faster than radio waves.
Ans: C
3. Which of the following has the shortest wavelength?
a) A photon of ultraviolet light.
b) Blue electromagnetic radiation.
c) An X-ray.
d) A radio wave.
e) Infrared radiation.
Ans: C
4. What is the main reason reflecting telescopes usually have a secondary mirror
in addition to a primary mirror?
a. To increase the light gathering power
b. To make the telescope shorter
c. To increase the focal length
d. To combat color changes due to bending the light
Ans: B
5. The major advantage CCDs have over other imaging techniques is that:
a. they have a higher quantum efficiency
b. they have a shorter integration time
c. they yield output in digital format
d. they operate at wavelengths we can’t see
e. All of the above are true
Ans: E
6. Why do astronomers want to build bigger telescopes?
A. To eliminate the effects of seeing.
B. To search for life on Mars.
C. To observe fainter or more distant objects.
Answer: C, Explanation: Option A is incorrect since seeing blurs the images for all telescopes,
regardless of their size. Option B is incorrect because any life on Mars would be too small to see
with any telescope.
7. Why do astronomers build telescopes on mountains?
A. To be closer to the objects they are observing.
B. To minimize the effects of the atmosphere.
C. To observe wavelengths such as X-rays or ultraviolet light.
Answer: B
Explanation: The shortened distance is completely negligible, so choice A is incorrect. Since the
telescope is still inside Earth’s atmosphere, choice C is incorrect; those wavelengths are
unobservable. Choice B is correct; being farther up in the atmosphere means less water vapor
which would cause distortion.
8. Imagine that you are the head of a funding agency that can afford to build one telescope.
Which of the following proposed telescopes would be best to support?
A. A radio telescope in orbit around Earth
B. An ultraviolet telescope in orbit around Earth
C. An X-ray telescope located in New Mexico
Ans: B