Name: __________________________  Date: _____________

1.	Electromagnetic radiation moving through space with the speed of light consists of	
A)	oscillating electric and magnetic fields moving in opposite directions along the same line in space.	
B)	oscillating magnetic fields that over time and distance change to oscillating electric fields and then back to magnetic fields in a continuous manner.	
C)	oscillating electric and magnetic fields, always inseparable, always having the same frequency and wavelength, and traveling in the same direction.	
D)	oscillating electric fields, with magnetic fields occasionally accompanying them, moving in the same direction.	

2.	What is the relationship between color and wavelength for light?	
A)	Wavelength increases from violet to yellow-green, then decreases again to red.	
B)	Wavelength decreases from violet to red.	
C)	Wavelength increases from violet to red.	
D)	Wavelength depends only on brightness and is independent of color.	

3.	In which of the following parameters does a photon of blue light NOT differ from a photon of yellow light, in a vacuum?	
A)	Energy	
B)	Color	
C)	Wavelength	
D)	Speed	

4.	What is the one fundamental difference between X rays and radio waves?	
A)	They always come from different sources.	
B)	Their wavelengths are very different.	
C)	Their speeds in outer space are different.	
D)	Radio waves are always wavelike, whereas X rays always behave like particles.	

5.	Our present understanding of the nature of light is that it	
A)	behaves only as a wave.	
B)	behaves only as a particle.	
C)	displays behavior of both waves and particles.	
D)	is completely different from both waves and particles.	

6.	Visible light occupies what position in the whole electromagnetic spectrum?	
A)	Between radio and infrared radiation	
B)	Between infrared and ultraviolet	
C)	Between infrared and microwave	
D)	Between ultraviolet and X rays	

7.	Which of the following wave effects is NOT electromagnetic in nature?	
A)	Gamma rays	
B)	Seismic waves	
C)	Microwaves	
D)	Radio waves	

8.	The two ranges of electromagnetic radiation for which the Earth's atmosphere is reasonably transparent are	
A)	X rays and visible radiation.	
B)	visible and radio radiation.	
C)	visible and far infrared radiation.	
D)	UV and radio waves.	

9.	The main reason for building large optical telescopes on the Earth's surface is	
A)	to bring astronomical objects closer for more detailed examination by scientists.	
B)	to collect more light from faint objects.	
C)	for national prestige, with no scientific reason.	
D)	to nullify the effects of the Earth's atmosphere and thus produce higher resolution photographs.	

10.	What is refraction of light?	
A)	The breaking of white light into its composite colors	
B)	The change in direction of a light ray as it reflects from a more dense material than the one in which it is traveling	
C)	The absorption of light as it traverses a dense, transparent material	
D)	The change in direction of a light ray as it passes at an angle from one transparent material to another which has a different optical density	

11.	A Newtonian telescope uses	
A)	only one mirror with its front surface shaped into a parabola.	
B)	one curved mirror and one flat mirror at a 45° angle to the first mirror axis.	
C)	two flat mirrors inclined to each other at a right angle.	
D)	two curved mirrors, one convex, the second concave in shape.	

12.	A Cassegrain reflecting telescope is constructed using a	
A)	concave primary mirror followed by a smaller convex secondary mirror that reflects light back through a hole in the primary mirror.	
B)	curved primary mirror followed by a series of both plane and curved mirrors that channel the light to a remote location fixed with respect to the Earth.	
C)	concave primary mirror and concave secondary mirror that reflects light back through a hole in the primary mirror.	
D)	concave primary mirror and a flat, diagonal secondary mirror mounted at a 45° angle to the telescope axis.	

13.	What is the magnification of a Newtonian telescope that has a primary mirror of diameter 0.25 m and focal length of 2 m when used with an eyepiece of focal length 25 mm and an optical diameter of 5 mm?	
A)	50 times	
B)	10 times	
C)	80 times	
D)	400 times	

14.	In general, doubling the diameter of an optical telescope will	
A)	quadruple the light-gathering power and double the angular resolution.	
B)	quadruple the light-gathering power and quadruple the angular resolution.	
C)	double both the light-gathering power and the angular resolution.	
D)	double the light-gathering power and quadruple the angular resolution.	

15.	What is a CCD (charge-coupled device)?	
A)	A detector in which a small electric current is controlled by a bimetallic strip that expands and contracts in response to infrared radiation	
B)	An electronic filter to single out one wavelength or set of wavelengths for studying astronomical objects	
C)	A device in which an image from a photographic plate or film is transferred to a computer by moving static electric charges directly into the computer memory in a manner similar to modern copying machines	
D)	An array of small light-sensitive elements that can be used in place of photographic film to obtain and store a picture	

16.	How does the speed of light in a substance such as glass compare to the speed of light in a vacuum?	
A)	The speed of light in glass is faster than the speed of light in a vacuum.	
B)	The speed of light is the same in both, equal to 299,792.458 km/s.	
C)	The speed of light in glass is slower than the speed of light in a vacuum.	
D)	The speed of light in glass can be faster or slower than the speed of light in a vacuum, depending on the type of glass.	

17.	What is the main optical element of a refracting telescope?	
A)	A plane (flat) mirror	
B)	A curved mirror	
C)	A prism	
D)	A lens	

18.	A refracting telescope has an objective lens of focal length 40 cm and a diameter of 10 cm, and an eyepiece of focal length 5 cm and diameter 1 cm. What is the magnifying power of this telescope?	
A)	10×	
B)	40×	
C)	2×	
D)	8×	

19.	What is the reason for the fact that a reflecting telescope used at prime focus does NOT suffer from chromatic aberration?	
A)	The aluminum coating on the mirror absorbs light from all wavelengths except the one of interest to the astronomer and this light is focused perfectly.	
B)	The light has passed through only one lens.	
C)	All wavelengths of light are reflected by the same amount irrespective of color.	
D)	The lens is perfectly formed such that all colors of light travel through the lens along the same path.	

20.	Which of the following types of telescopes is most seriously affected by chromatic aberration?	
A)	A radio telescope	
B)	A refracting telescope	
C)	A Newtonian telescope	
D)	A Cassegrain telescope	

21.	A spherical mirror suffers from spherical aberration because	
A)	different colors are focused at different distances from the mirror.	
B)	a mirror of this shape is structurally weak and will sag under its own weight, distorting the image.	
C)	the starlight is distorted by turbulence in the Earth's atmosphere.	
D)	different parts of the mirror focus the light at different distances from the mirror.	

22.	The major cause of blurring and unsharp images of objects observed through very large telescopes, at the extreme limit of magnification, is	
A)	the poor tracking capabilities of modern telescopes.	
B)	the poor optical polish achievable on large mirrors.	
C)	the clumsiness of the telescope operator.	
D)	air turbulence in the Earth's atmosphere.	

23.	The best Earth-based sites for modern large astronomical telescopes, which provide the least seeing effects upon astronomical images, are	
A)	near large cities, where the warm air from human activity serves to stabilize the overlying atmosphere.	
B)	at sea level, where the air is less turbulent.	
C)	on the downwind side of mountain ranges, where smooth airflow produces clear air and stable images.	
D)	on the tops of high mountains, above a large fraction of the disturbing atmosphere.	

24.	Why was adaptive optics developed?	
A)	To prevent the distortion of mirrors by the vacuum of space	
B)	To compensate for image distortion caused by the Earth's atmosphere	
C)	To compensate for spherical aberration	
D)	To prevent distortion by sagging in very thin, lightweight mirrors	

25.	How does angular resolution for a given diameter of telescope depend on wavelength?	
A)	Angular resolution worsens as wavelength increases.	
B)	Angular resolution may improve or worsen as wavelength increases, depending on other factors such as intensity and spectral range (e.g., optical, infrared, radio).	
C)	Angular resolution improves as wavelength increases.	
D)	Angular resolution depends only on the diameter of the telescope and is independent of wavelength.	

26.	The main reason that the angular resolution of a 20-m diameter radio telescope is worse than that of a 0.5-m diameter optical telescope is that	
A)	angular resolution gets worse as wavelength decreases.	
B)	angular resolution gets worse as wavelength increases.	
C)	an optical mirror suffers from chromatic aberration.	
D)	angular resolution gets worse as mirror size increases.	

27.	How is interferometry used in radio astronomy?	
A)	Signals from a radio source are combined with an equivalent signal delayed in time to produce interference, thereby increasing the angular resolution of the telescope.	
B)	Signals from different places around the dish of a radio telescope are combined to produce interference and increase the angular resolution of the telescope.	
C)	Signals from two or more different radio telescopes are combined to produce a single image of greater angular resolution than from any one telescope alone.	
D)	Signals from different parts of a radio source are combined to increase the angular resolution of the telescope.	

28.	Telescopes are placed in space to view distant galaxies primarily	
A)	to get closer to the observed objects.	
B)	to avoid the absorption and distortion of the light or other radiations within the atmosphere of the Earth.	
C)	to avoid having to steer the telescope against the Earth's motion.	
D)	to avoid the light pollution from the Earth's populated areas.	

Answer Key

1.	C	
2.	C	
3.	D	
4.	B	
5.	C	
6.	B	
7.	B	
8.	B	
9.	B	
10.	D	
11.	B	
12.	A	
13.	C	
14.	A	
15.	D	
16.	C	
17.	D	
18.	D	
19.	C	
20.	B	
21.	D	
22.	D	
23.	D	
24.	B	
25.	A	
26.	B	
27.	C	
28.	B