Deck 4: Light and Telescopes

Question 1

Radio telescopes are important in astronomy because

A) they can detect cool hydrogen.
B) they have high magnification.
C) the can detect interstellar dust clouds.
D) they are very inexpensive to build on tops of mountains.
E) they don t need to be as large as optical telescopes to achieve the same resolving power.

Answer 1

they can detect cool hydrogen.

Question 2

The technique of connecting multiple telescopes together to combine the images from each telescope is known as

A) abberation.
B) resolving power.
C) active optics.
D) adaptive optics.
E) interferometry.

Answer 2

interferometry.

Question 3

What is the wavelength of the longest wavelength light that can be seen with the human eye?

A) 400 nm
B) 4000 nm
C) 7000 nm
D) 700 nm
E) 3 10 8 m

Answer 3

700 nm

Question 4

The sidereal drive of a telescope mounting must turn the telescope

A) southward about the polar axis.
B) eastward about the polar axis.
C) westward about the polar axis.
D) northward about the polar axis.
E) none of the above

Question 5

The energy of a photon

A) is proportional to the wavelength of the light.
B) is inversely proportional to the wavelength of the light.
C) depends only on the speed of the light.
D) depends only on the mass of the photon.
E) depends on both the mass and speed of the photon.

Question 6

The ____ of a telescope is a measure of its ability to show fine detail and depends on the diameter of the objective.

A) light-gathering power
B) focal length
C) magnifying power
D) resolving power
E) spherical aberration

Question 7

Astronomers build telescopes on tops of mountains because

A) there is less air to dim the light.
B) the seeing is better.
C) CCDs work better when there is less oxygen in the air.
D) all of the above
E) a and b

Question 8

____ has (have) wavelengths that are shorter than visible light.
I. Gamma-rays
II. Ultraviolet light
III. Infrared radiation
IV. X-rays

A) I II
B) I, IV
C) II III
D) II, III, IV
E) I, II, IV

Question 9

Ultraviolet radiation from a star

A) will not penetrate Earth s atmosphere and reach the ground.
B) has a wavelength that is longer than the visible light emitted by the star.
C) has a wavelength that is shorter than the x-rays emitted by the star.
D) a and b
E) b and c

Question 10

A ____ is a piece of glass with many small parallel lines etched on its surface to produce a spectrum.

A) grating
B) spectrograph
C) photometer
D) charge-coupled device
E) prism

Question 11

A new generation of ground-based telescopes is currently being built that overcomes the limitations of the older large telescopes. Some of these new telescopes

A) use segmented mirrors.
B) use mirrors that are very thin.
C) use active optics to control the shape of the mirror.
D) all of the above.
E) none of the above

Question 12

A telescope that suffers from chromatic aberration and has a low light gathering power is most likely

A) a small diameter reflecting telescope.
B) a small diameter refracting telescope.
C) a large diameter refracting telescope.
D) a large diameter reflecting telescope.
E) an infrared telescope.

Question 13

Interferometry

A) is used to improve the resolving power.
B) decreases the chromatic aberration of a telescope.
C) works only for large x-ray and ultraviolet telescopes.
D) requires that radio telescopes be within a few hundred feet of each other.
E) none of the above

Question 14

A ____ has a few million light sensitive diodes in an array typically about a half-inch square.

A) photometer
B) charge-coupled device
C) spectrograph
D) photographic plate
E) grating

Question 15

The Very Long Baseline Interferometer (VLBI)

A) is the highest resolution optical telescope ever built.
B) is located in Arecibo, Puerto Rico.
C) is a matched pair of 8 m telescopes, one of which is in Chile and the other in Hawaii.
D) is an air-borne infrared telescope.
E) is a set of radio telescopes linked together electronically to provide very high resolution.

Question 16

____ has (have) wavelengths that are longer than visible light.

A) Gamma-rays
B) Ultraviolet light
C) Infrared radiation
D) X-rays
E) a, b and d above

Question 17

Long wavelength visible light

A) will have a greater energy than short wavelength visible light.
B) will have a speed that is faster than short wavelength light.
C) has a higher frequency than short wavelength visible light.
D) will appear blue in color to the average human eye.
E) will appear red in color to the average human eye.

Question 18

Radio telescopes have poor resolving power because

A) their diameters are so large.
B) the energy they receive is not electromagnetic radiation.
C) radio waves have long wavelengths.
D) a and b
E) none of the above

Question 19

Which of the following telescopes must be used above Earth s atmosphere?

A) an optical telescope
B) the VLBI telescope
C) an x-ray telescope
D) a radio telescope
E) none of the above

Question 20

Far infrared astronomy must be done from high-flying aircraft because

A) far infrared radiation is absorbed low in Earth s atmosphere.
B) far infrared photons are quite energetic.
C) far infrared telescopes are not very heavy.
D) far infrared sources are very bright.
E) none of the above

Question 21

Photons of blue light

A) have a greater energy than photons of red light.
B) have a greater energy than photons of ultraviolet light.
C) have a lower frequency than photons of red light.
D) have a longer wavelength than photons of red light.
E) travel at a greater speed than photons of red light.

Question 22

What is the frequency of the shortest wavelength light that can be detected by the average human eye?

A) 0.0025 Hz
B) 7.5*10¹⁴ Hz
C) 3.0*10⁸ m/sec
D) 700 nm
E) 400 nm

Question 23

Segmented mirrors sag under their own weight. Their optical shape must be controlled by computer-driven thrusters under the mirrors in what is called

A) an achromatic lens.
B) active optics.
C) a Schmidt-Cassegrain design.
D) a Newtonian design.
E) interferometry.

Question 24

Which of the following types of electromagnetic radiation has the highest frequency?

A) x-rays
B) visible light
C) radio
D) gamma-rays
E) infrared radiation

Question 25

The resolving power of an optical telescope with a diameter of 232 cm is

A) 0.05 arc seconds.
B) 232 arc seconds.
C) 2.32 arc seconds.
D) 5 arc seconds.
E) 11.6 arc seconds.

Question 26

Blue light differs from red light in that

A) blue light has a higher energy than red light.
B) blue light has a lower energy than red light.
C) blue light has a shorter wavelength than red light.
D) blue light has a longer wavelength than red light.
E) More than one of the above.

Question 27

Which of the following types of electromagnetic radiation has the smallest frequency?

A) x-rays
B) visible light
C) radio
D) gamma-rays
E) infrared radiation

Question 28

What is the wavelength of light that has a frequency of 3 MHz?

A) 9*10¹⁴Hz
B) 1*10¹⁴ m
C) 9*10¹⁴m
D) 100 m
E) 0.01 m

Question 29

Which of the following features of a telescope determines its light gathering power?

A) The focal length of the objective
B) The focal length of the eyepiece
C) The diameter of the objective
D) Length of the telescope tube
E) None of the above.

Question 30

Which of the following types of electromagnetic radiation has the greatest energy?

A) x-rays
B) visible light
C) radio
D) gamma-rays
E) infrared radiation

Question 31

A nanometer is

A) a unit of frequency.
B) a unit of energy.
C) a unit of mass.
D) a unit of length.
E) a unit of resolving power.

Question 32

An achromatic lens

A) is used to correct spherical aberration in reflecting telescopes.
B) is used to correct chromatic aberration in refracting telescopes.
C) is used to correct spherical aberration in refracting telescopes.
D) is used to correct chromatic aberration in reflecting telescopes.
E) contains two mirrors and focuses the light back through the primary mirror.

Question 33

____ is absorbed by water in Earth s atmosphere and requires that telescopes for observing at these wavelengths be placed on mountain tops or in space.

A) Infrared radiation
B) Ultraviolet radiation
C) Radio wave radiation
D) X-ray radiation
E) Visible light

Question 34

What is the magnification of a telescope and eyepiece if the telescope objective has a focal length of 200 cm and the eyepiece has a focal length of 2.0 cm

A) 400 times
B) 4000 times
C) 100 times
D) 1000 times
E) 40 times

Question 35

The pupil of the human eye is approximately 0.8 cm in diameter when adapted to the dark. The ratio of the light gathering power of a 1.6 m telescope to that of the human eye is ____.

A) 2
B) 4
C) 20
D) 400
E) 40,000

Question 36

____ is absorbed by ozone in Earth s atmosphere that is located betweeN₂0 km and 40 km above Earth s surface. Therefore, telescopes to observe this radiation must be placed in space.

A) Infrared radiation
B) Ultraviolet radiation
C) Radio wave radiation
D) X-ray radiation
E) Visible light

Question 37

Increasing the diameter of a telescope
I. increases its light gathering power.
II. increases its resolving power.
III. increases it magnifying power.
IV. increases its chromatic aberration.

A) I, II, III, IV
B) I, II, III
C) I, II, IV
D) III IV
E) I II

Question 38

The objective of most radio telescopes is similar to the objective of a reflecting optical telescope in that

A) they are both concave in shape
B) they are both convex in shape
C) they are typically the same size
D) they are both made of metal.
E) they have nothing in common.

Question 39

Which of the following types of electromagnetic radiation has the lowest energy?

A) x-rays
B) visible light
C) ultraviolet
D) gamma-rays
E) infrared radiation

Question 40

What is the ratio of the light gathering power of a 10 m telescope to that of a 1 m telescope?

A) 10 to 1
B) 1 to 10
C) 100 to 1
D) 1 to 100
E) 3.2 to 1

Question 41

The figure below shows a single lens with two rays of white light incident on it from the left. Sketch the paths of the blue, yellow, and red components of each of these rays to the point where the light from the upper and lower rays would meet.

Question 42

A(n) ____________________ telescope has an objective that is a lens.

Question 43

In which way does a photon of blue light NOT differ from a photon of red light?

A) Energy
B) Speed
C) Wavelength
D) Color
E) Frequency

Question 44

What is the relationship between color and wavelength for light?

A) Wavelength increases from blue light to red light
B) Wavelength decreases from blue light to red light
C) All colors of light have the same wavelength.
D) Wavelength depends on intensity not color.

Question 45

The diagram below illustrates the layout and light path of a reflecting telescope of the ____________________ design.

Question 46

A(n) ____________________ is used to measure the brightness and color of stars.

Question 47

The resolving power of a telescope is ____.

A) a measure of the minimum angular separation that can be seen with the telescope.
B) a measure of the maximum angular separation that can be seen with the telescope.
C) a measure of the amount of light that the telescope can gather in one second.
D) the separation between the objective and the image.
E) a measure of how blurry object appear in the telescope.

Question 48

A telescope whose objective is a lens and contains no mirrors is a(n) ____ telescope.

A) Refracting
B) Reflecting
C) Deflecting
D) Compound
E) Retracting

Question 49

The largest single dish radio telescope is ____ .

A) suspended on cables in a valley
B) buried deep in a mine underground
C) orbiting in space
D) suspended from balloons in the upper atmosphere

Question 50

Which of the following sequences of electromagnetic radiation is correct in order of increasing energy?

A) Gamma rays, X-rays, infrared, radio
B) Radio, microwave, gamma rays, UV
C) Visible, UV, X-rays, gamma rays
D) Visible, microwave, radio, infrared
E) Infrared, visible, radio, X-rays

Question 51

The main reason for positioning many radio telescopes across a large area and combining the signals is

A) to observe more objects in a shorter amount of time.
B) provide a backup system if one or more of the telescopes go down.
C) to produce higher resolution images.
D) to avoid interference between signals from the separate telescopes.
E) to account for the motion of objects in the sky as a result of the Earth s rotation.

Question 52

Radio telescopes are ____ telescopes.

A) Reflecting
B) Refracting
C) Deflecting
D) Compound
E) Retracting

Question 53

Refracting telescopes suffer from ____________________ aberration.

Question 54

In a reflecting telescope the objective is a ____.

A) prism
B) mirror
C) lens
D) diffraction grating
E) photographic plate

Question 55

Chromatic aberration occurs in a ____ telescope when ____.

A) reflecting; different colors of light do not focus at the same point.
B) refracting; different colors of light do not focus at the same point.
C) reflecting; light of different wavelengths get absorbed by the mirror.
D) refracting; light of different wavelengths get absorbed by the lens.

Question 56

The main reason for building large optical telescopes on the Earth s surface is

A) that there is a lot of money in science that needs to get spent.
B) to collect as much light as possible from faint objects.
C) to nullify the blurring effects of the Earth s atmosphere and thus produce higher resolution images.
D) to bring astronomical objects closer to make them brighter.
E) that the warm temperatures of the Earth s surface allow for easier telescope operation.

Question 57

The light-gathering power of a telescope is directly proportional to

A) the diameter of the primary mirror or lens.
B) the focal length of the primary mirror or lens.
C) the ratio of the focal lengths of its primary mirror or lens and its eyepiece.
D) the length of the telescope tube.
E) the diameter of the eyepiece.

Question 58

What statement below best describes the refraction of light?

A) The absorption of light as it travels though a dense, transparent material.
B) The spreading out of white light according to wavelength.
C) The change in direction of a light ray as it passes to a medium of different optical density.
D) The change in direction of a ray of light as it reflects off a surface.

Question 59

A wave on a lake is found to have a wavelength of 2 m and a frequency of 0.3 Hz. What is the speed of this wave?

Question 60

Which has the larger light-gathering power?

A) A telescope of 5 cm diameter and focal length of 50 cm.
B) A telescope of 6 cm diameter and focal length of 100 cm.
C) A telescope of 2 cm diameter and focal length of 100 cm.
D) A telescope of 3 cm diameter and focal length of 75 cm.
E) Both b and c since they have the same focal length.

Question 61

300 nm light has a lower frequency than 500 nm light.

Question 62

The largest optical telescope ever constructed was a refracting telescope.

Question 63

Interferometry is easiest to use with telescopes that observe at very short wavelengths.

Question 64

Reflecting telescopes are no longer popular with astronomers because they are expensive and suffer from chromatic aberration.

Question 65

The light-gathering power of a telescope increases as the size of the objective increases.

Question 66

The amount of energy a photon carries depends on its wavelength.

Question 67

One of the advantages of charge-coupled devices over photographic plates is that a CCD can record bright and faint objects on the same exposure.

Question 68

The main lens or mirror of a telescope is called the ____________________.

Question 69

The ____________________ is a measure of how many times larger the angular size of an object appears through a telescope.

Question 70

The sidereal drive on a telescope mounting must turn the telescope eastward about the polar axis.

Question 71

The ____________________ of a telescope is determined by the size of the objective.

Question 72

X-rays easily penetrate Earth s atmosphere and reach the ground from space.

Question 73

A(n) ____________________ uses a mirror as its objective.

Question 74

The ____________________ is a measure of the clarity of the atmosphere.

Question 75

The ____________________ is a measure of the finest detail that can be seen in an image.

Question 76

Telescopes observing in the far ultraviolet can work from high-flying aircraft.

Question 77

All radio telescopes are refracting telescopes.

Question 78

Light can behave as a particle or as a wave.

Question 79

The process of combining signals from separate telescopes to improve resolution is called ____________________.

Question 80

In a reflecting telescope, the objective is a mirror.