Question 1

If a laser light pulse was sent toward the Moon and some of this light were to be reflected toward Earth from retroreflectors left on the Moon by astronauts, how long after the transmission of the initial flash would the reflected light be detected through a telescope on Earth?

Accepted Answer

A)  2.56 microseconds 
B)  2.56 seconds 
C)  1.28 seconds 
D)  1.28 milliseconds

Question 2

Which characteristic property of a glass lens is the MOST important in bending light rays to form a focused image?

Accepted Answer

A)  color of the glass 
B)  curvature and shape of its surfaces 
C)  thickness of the center of the lens 
D)  diameter or size of the lens

Question 3

How can one increase the magnification of a refracting telescope without decreasing the light-gathering power?

Accepted Answer

A)  Decrease both the diameter and the focal length of the objective lens. 
B)  Increase the focal length of the eyepiece. 
C)  Decrease the focal length of the eyepiece. 
D)  Increase the diameter of the eyepiece.

Question 4

What causes chromatic aberration in the objective lens of a telescope?

Accepted Answer

A)  Reflection of light back and forth inside the lens produces multiple images and the overall combination of the images will be distorted. 
B)  Different colors are refracted through different angles at each surface of the lens. 
C)  Different colors suffer different amounts of absorption by the glass in the lens. 
D)  The shape of the lens surface distorts the image.

Question 5

In a modern neutrino detector, neutrinos

Accepted Answer

A)  are detected directly by photomultipliers that emit an electrical signal when struck by a neutrino. 
B)  strike water molecules, converting them into molecules of heavy water that then sink to the bottom of the tank. 
C)  cause reactions that emit Cherenkov radiation that is then detected with photomultipliers. 
D)  that have electric charge are focused by a series of magnets to produce an intense beam that can be detected more easily by conventional detectors.

Question 6

A ray of light enters a spherical lens. The effective focal length of the lens is determined by each of these EXCEPT

Accepted Answer

A)  the curvature of the lens. 
B)  the distance from the center line at which the ray enters the lens. 
C)  the placement of the eyepiece. 
D)  the wavelength of the light.

Question 7

In a Cherenkov radiation detector a neutrino

Accepted Answer

A)  passing through water is slowed down and emits a flash of light. 
B)  interacts with a deuterium nucleus, forcing the emission of an electron that moves faster than light in water and emits a flash of light. 
C)  interacts with a hydrogen atom forcing it to move rapidly through water and emit a flash of light. 
D)  strikes a photomultiplier, causing it to emit a flash of light.

Question 8

What characteristic of the 10-m Keck telescopes makes them fundamentally different from older telescopes, such as the one on Mount Palomar?

Accepted Answer

A)  They are located in Earth's orbit, away from all the distortions of Earth's atmosphere. 
B)  They are actually four closely spaced telescopes that can be operated together as if they were a single telescope. 
C)  The primary mirrors are large, very thin pieces of glass that can be deformed rapidly to compensate for seeing. 
D)  The primary mirror is made up of 36 separate mirror segments.

Question 9

Charge-coupled devices (CCDs) are used in all of these EXCEPT

Accepted Answer

A)  telescopes. 
B)  picture-taking cell phones. 
C)  digital cameras. 
D)  long-exposure film photography.

Question 10

The first astronomical radio source was detected and identified in the year

Accepted Answer

A)  1897. 
B)  1945. 
C)  1967. 
D)  1932.

Question 11

A department store sells an "astronomical telescope" with an objective lens of 30-cm focal length and a diameter of 5 cm, and an eyepiece lens of focal length 5 mm and diameter 4 mm. What is the magnifying power of this telescope?

Accepted Answer

A)  6× 
B)  150× 
C)  60× 
D)  12.5×

Question 12

Which of these characteristics of an astronomical telescope is the MOST important for determining the angular resolution?

Accepted Answer

A)  magnifying power of the telescope 
B)  focal length of the objective lens or mirror 
C)  focal length of the eyepiece 
D)  diameter of the objective lens or mirror

Question 13

One major difference between radio waves and light is that

Accepted Answer

A)  light waves are electromagnetic, whereas radio waves are not. 
B)  radio waves are electromagnetic, whereas light waves are not. 
C)  radio waves have shorter wavelength than light waves. 
D)  radio waves have longer wavelength than light waves.

Question 14

Which of these sequences of electromagnetic radiation is correct, in order of increasing energy of the photons (or quanta)?

Accepted Answer

A)  visible light, microwave, radio wave, infrared 
B)  radio wave, microwave, gamma ray, UV 
C)  visible light, UV radiation, X-ray, gamma ray 
D)  gamma ray, radio wave, X-rays, infrared

Question 15

How is chromatic aberration MOST often corrected in a modern refracting telescope?

Accepted Answer

A)  by using a combination of two lenses made from different types of glass 
B)  by painting the inside of the telescope jet black to minimize reflections 
C)  by grinding the lens surfaces into a parabolic shape 
D)  by using a prism to recombine the colors into white light

Question 16

If a person creates a spectrum with a prism as Newton did and then probes the temperature with thermometers that they have kept in the dark, they will find the thermometer will show a temperature rise when placed

Accepted Answer

A)  in the visible part of the spectrum but nowhere else. 
B)  in the visible part of the spectrum and in the invisible region just beyond the red but nowhere else. 
C)  in the visible part of the spectrum and in the invisible region just beyond the violet but nowhere else. 
D)  anywhere from the invisible region beyond the red, through the visible, through the invisible region beyond the violet.

Question 17

The main absorber in the atmosphere for infrared radiation, which impedes observations of astronomical infrared objects, is

Accepted Answer

A)  water vapor, H2O. 
B)  nitrogen and oxygen (N2 and O2), the major constituents of the atmosphere. 
C)  electrons and ionized atoms in Earth's ionosphere. 
D)  dust.

Question 18

The neutrino is

Accepted Answer

A)  a heavy, uncharged nuclear particle, easily detected. 
B)  another name for an electron that carries a positive charge instead of a negative charge. 
C)  a very small asteroidlike body orbiting the Sun. 
D)  an elusive, subatomic particle having little mass which is difficult to detect.

Question 19

What is the main reason for using several radio telescopes together as an interferometer?

Accepted Answer

A)  to obtain much better angular resolution or sharpness in the images 
B)  to ensure that at least one of the telescopes is in a radio-interference-free zone 
C)  to collect more radiation from very faint sources 
D)  to ensure that observations are uninterrupted by the failure of one or two telescopes

Question 20

In the 1860s, James Clerk Maxwell carried out important investigations on the nature of light when he

Accepted Answer

A)  demonstrated the wave nature of light by passing light through two slits and obtained a pattern of bright and dark bands on a screen that he correctly interpreted as interference between the two light beams. 
B)  demonstrated that white light was made up of colors that could be split by a prism and that these colors were not produced by the glass through which the light passed. 
C)  proved mathematically that light could be described by oscillating electric and magnetic fields. 
D)  showed that a prism through which light passed added a spectrum of colors to the light.

Exam 3: Light and Telescopes