Deck 4: Light and Telescopes

Question 1

The total number of neutrons and protons determine the type of chemical element it is.

Answer 1

False

Question 2

The highest spatial resolution images that we have of many planets' surfaces come from the Hubble Space Telescope.

Answer 2

False

Question 3

Moving charges produce magnetic fields.

Answer 3

True

Question 4

The image quality of most optical telescopes is limited by differential atmospheric refraction experienced by light as it passes through the Earth's atmosphere.

Question 5

In the past,astronomers have placed telescopes in highflying aircraft in an effort to rise above the water vapor in the Earth's atmosphere.

Question 6

A radio photon travels more slowly than a gamma ray photon.

Question 7

The energy of a photon is inversely proportional to its wavelength.

Question 8

Electric fields are created by charged particles.

Question 9

It is possible for light to travel slower than 300,000 km/s.

Question 10

The image below shows an example of a refracting telescope.

Question 11

How faint an object we can see with our eyes is limited only by the integration time of our eye (how often it processes input).

Question 12

How does the speed of light traveling through a medium (such as air or glass)compare to the speed of light in a vacuum?

A) It is the same as the speed of light in a vacuum.
B) It is always less than the speed of light in a vacuum.
C) It is always greater than the speed of light in a vacuum.
D) Sometimes it is greater than the speed of light in a vacuum,and sometimes it is less,depending on the medium.

Question 13

One of the reasons why the Hubble Space Telescope has better spatial resolution than a 4-m ground-based telescope is that it has a larger mirror.

Question 14

The 305-m Arecibo radio telescope has a resolution that is no better than that of the human eye.

Question 15

The image below shows the Very Large Array in New Mexico.Radio telescopes are often used in interferometric arrays to increase light gathering power.

Question 16

Chromatic aberration is a problem that limits the image quality of reflecting telescopes.

Question 17

The speed of light was first determined by which scientist?

A) Galileo
B) Rømer
C) Kepler
D) Newton
E) Einstein

Question 18

The light-year is a unit of:

A) time
B) distance
C) speed
D) energy

Question 19

The speed of light in a vacuum is __________.

A) 300,000 m/s
B) 300,000 mph
C) 300,000 km/s
D) 300,000,000 mph
E) infinite

Question 20

Astronomers usually study distant objects by looking at them directly through the eyepiece of a telescope.

Question 21

How does the resolution of a telescope depend on its focal length?

A) The longer the focal length,the better the resolution.
B) The longer the focal length,the worse the resolution.
C) There is no relation between resolution and focal length.

Question 22

One reason to prefer a reflecting over a refracting telescope is its:

A) lack of chromatic aberration.
B) shorter length for the same aperture size.
C) lighter weight for larger apertures.
D) All of the above are valid reasons.

Question 23

As a beam of light travels from one medium to another,the change in direction of the beam of light depends on:

A) the wavelength of the light
B) the index of refraction of the medium through which it is traveling
C) the index of refraction of the medium into which it is moving
D) all of the above

Question 24

A red photon has a wavelength of 650 nm.An ultraviolet photon has a wavelength of 250 nm.The energy of an ultraviolet photon is __________ than a red photon.

A) 2.6 times larger
B) 6.8 times larger
C) 2.6 times smaller
D) 6.8 times smaller

Question 25

Which of the following photons carry the least amount of energy?

A) A blue photon of the visible spectrum,whose wavelength is 450 nm
B) An infrared photon,whose wavelength is 10^-5 m
C) A red photon in the visible spectrum,whose wavelength is 700 nm
D) A microwave photon,whose wavelength is 10^-2 m

Question 26

As wavelength increases,the energy of a photon __________ and its frequency __________.

A) increases; decreases
B) increases; increases
C) decreases; decreases
D) decreases; increases

Question 27

Using the figure below,which type of electromagnetic wave has a wavelength of approximately 10⁻⁵ m?

A) X-rays
B) Infrared
C) Microwave
D) Radio

Question 28

The major advantage CCDs have over other imaging techniques is that:

A) they have a higher quantum efficiency
B) they have a linear response to light
C) they yield output in digital format
D) they operate at visible and near-infrared wavelengths
E) All of the above are true

Question 29

Before CCDs were invented,what was the device most commonly used for imaging with optical telescopes?

A) Polaroid cameras
B) Photographic glass plates
C) High-speed film
D) Video cameras

Question 30

Why is an iron atom a different element than a sodium atom?

A) A sodium atom has fewer neutrons in its nucleus than an iron atom.
B) An iron atom has more protons in its nucleus than a sodium atom.
C) A sodium atom is bigger than an iron atom.
D) All of the above are true.

Question 31

The fact that the speed of light is constant (as it travels through a vacuum)means that:

A) photons with longer wavelengths have lower frequencies
B) radio wave photons have shorter wavelengths than gamma ray photons
C) X-rays can be transmitted through the atmosphere around the world
D) All of the above are true

Question 32

Which of the following lists different types of electromagnetic radiation in order of increasing wavelength?

A) Radio waves,infrared,visible,ultraviolet,X-rays
B) Gamma rays,ultraviolet,visible,infrared,radio waves
C) Gamma rays,X-rays,infrared,visible,ultraviolet
D) X-rays,infrared,visible,ultraviolet,radio waves
E) Radio waves,ultraviolet,visible,infrared,gamma rays

Question 33

Photography provides an improvement over naked-eye observations because:

A) it is possible to observe a larger field of view with photographic plates
B) the quantum efficiency is higher for photographic plates
C) the image resolution is much better for photographic plates
D) it is possible to detect fainter objects with the use of photographic plates

Question 34

Which telescope would collect 100 times more light than a 1-m telescope?

A) 100-m telescope
B) 50-m telescope
C) 30-m telescope
D) 10-m telescope

Question 35

The part of the human eye that acts as the detector is the:

A) retina
B) pupil
C) rods
D) cones

Question 36

Light with a wavelength of 600 nm has a frequency of:

A) 5.0 × 10⁶ Hz
B) 5.0 × 10¹⁴ Hz
C) 5.0 × 10¹¹ Hz
D) 2.0 × 10¹⁵ Hz

Question 37

A prism is able to spread white light out into a spectrum of colors based on the property of:

A) reflection
B) refraction
C) dispersion
D) interference

Question 38

The light-gathering power of a 4-m telescope is __________ than that of a 2-m telescope.

A) 8 times larger
B) 4 times larger
C) 16 times smaller
D) 2 times smaller

Question 39

Why do 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 chromatic aberration

Question 40

How do the wavelength and frequency of red light compare to the wavelength and frequency of blue light?

A) Red light has a longer wavelength and higher frequency than those of blue light.
B) Red light has a longer wavelength and lower frequency than those of blue light.
C) Red light has a shorter wavelength and higher frequency than those of blue light.
D) Red light has a shorter wavelength and lower frequency than those of blue light.

Question 41

Arrays of radio telescopes can produce much better resolution than single-dish telescopes because they work based on the principle of:

A) reflection
B) refraction
C) diffraction
D) interference

Question 42

Explain why chromatic aberration is a problem for refracting mirrors but not reflecting mirrors.

Question 43

The angular resolution of a ground-based telescope is usually set by:

A) diffraction
B) refraction
C) the focal length
D) atmospheric seeing

Question 44

Ultraviolet radiation is hard to observe primarily because:

A) the Earth's atmosphere easily absorbs it
B) no space-based telescopes operate at ultraviolet wavelengths
C) only the lowest mass stars emit ultraviolet light
D) very few objects emit at ultraviolet wavelengths

Question 45

Which of the following causes the biggest problem in detecting infrared photons from an astronomical object?

A) Smog
B) Carbon dioxide
C) Water vapor
D) Light pollution

Question 46

Compare and contrast the wavelengths,frequencies,speeds,and energies of red and blue photons.

Question 47

If the wavelength of a beam of light were to double,how would that affect its frequency?

A) The frequency would be four times larger.
B) The frequency would be two times larger.
C) The frequency would be two times smaller.
D) The frequency would be four times smaller.
E) There is no relationship between wavelength and frequency.

Question 48

The SETI project's Allen Telescope Array will have 350 radio dishes,each with an individual diameter of 6 m,spread out over a circle whose diameter is 1 km.What would this array's spatial resolution be when it operates at 6,000 MHz?

A) 10 arcsec
B) 0.10 arcsec
C) 10 arcmin
D) 1.0 arcmin

Question 49

The 305-m Arecibo radio telescope in Puerto Rico has a resolution that is closest to that of:

A) the Hubble Space Telescope (0.1 arcsec)
B) a human eye (1 arcmin)
C) the Chandra X-ray Telescope (0.5 arcsec)
D) a 1-m optical telescope (1 arcsec)

Question 50

Which formula denotes how the speed of light is related to its wavelength and frequency?

A) c = $\lambda$ f
B) c = $\lambda$ /f
C) c = f/ $\lambda$
D) c = 1/ $\lambda$ f

Question 51

The angular resolution of the largest single-dish radio telescope in the United States,the 300-ft Green Bank Telescope,is __________ when it operates at a wavelength of 20 cm.

A) 0.12°
B) 0.12 arcmin
C) 0.12 arcsec
D) 12 arcsec

Question 52

The two Keck 10-m telescopes,separated by a distance of 85 m,can operate as an interferometer.What is its resolution when it observes in the infrared at a wavelength of 2 microns?

A) 0.01 arcsec
B) 0.006 arcsec
C) 0.05 arcsec
D) 0.2 arcsec

Question 53

Explain why the largest telescopes are not refracting telescopes.

Question 54

Using the figure below,which type of electromagnetic wave has a frequency of approximately 3 × 10¹⁷ Hz?

A) X-rays
B) Infrared
C) Microwave
D) Radio

Question 55

Cameras that use adaptive optics provide higher spatial resolution images primarily because:

A) they operate above the Earth's atmosphere
B) they capture infrared light,which has a longer wavelength than visible light
C) deformable mirrors are used to correct the blurring due to the Earth's atmosphere
D) composite lenses correct for chromatic aberration

Question 56

When we determine the angular resolution of an interferometric array of radio telescopes using the formula $\varTheta\varpropto\lambda$ /D,the variable D stands for the:

A) diameter of the telescopes
B) separation between the telescopes
C) number of telescopes
D) focal length of the telescopes

Question 57

A spaceship approaches Earth at 0.9 times the speed of light and shines a powerful searchlight onto Earth.How fast will the photons from this searchlight be moving when they hit Earth?

Question 58

Compare the light-gathering power of the human eye to that of a 10-inch telescope.

Question 59

The diffraction limit of a 4-m telescope is __________ than that of a 2-m telescope.

A) 2 times larger
B) 4 times larger
C) 2 times smaller
D) 4 times smaller

Question 60

The Voyager I spacecraft is currently 16.5 billion km from Earth and heading out of our Solar System.How long does it take radio messages from Voyager I to reach us?

A) 1.5 days
B) 15 hours
C) 1.5 weeks
D) 15 minutes

Question 61

What is the angular resolution of a 1-m,ground-based,optical telescope that observes at a wavelength of 600 nm compared to that of a 300-ft,single dish radio telescope that observes at a wavelength of 21 cm?

Question 62

Using the figure below,list the different types of electromagnetic waves in order of increasing frequency.

Question 63

Explain why stars twinkle when viewed from the ground.Would they twinkle if viewed from outer space?

Question 64

Discuss two tools that modern astronomers use to explore the cosmos that are different from traditional optical telescopes,and give an example of how and why each is used.

Question 65

The image below shows the Very Large Array in New Mexico.What is the benefit of using multiple telescopes in such an array?

Question 66

What type of telescope is shown in the image below?

Question 67

Explain how adaptive optics help compensate for atmospheric seeing.

Question 68

Using the figure below,list the different types of electromagnetic waves in order of increasing wavelength.

Question 69

Explain two major advantages of CCDs over other imaging techniques.

Question 70

What is the diffraction limit of a 4-m telescope observing at a wavelength of 650 nm?

Question 71

Calculate the resolution of an interferometric array consisting of five 10-m radio telescopes,each located 1,000 meters apart from each other and observing a distant object at a wavelength of 21 cm.