Directions (1-5): Read the following paragraph. Some of the words have been highlighted in bold. Answer the questions based on this paragraph.
Light has been used as a beacon to mariners for thousands of years, for as long as man has taken to the sea. From the first primitive light beacons evolved the modern lighthouse, found on almost every waterway and coast in the world. To the uneducated eye each of these lighthouses, despite their distinct locations, seem to be irrelevant variations on a homogeneous design. However, nothing could be further from the truth; from height to lenses, each lighthouse is as unique as the landscape that surrounds it.
There is not one feature of a lighthouse that is arbitrary. By day, the varying color patterns painted on lighthouses help sailors distinguish their location along the coastline. These patterns, known as “daymarks,” are usually a combination of white, black, or red, can be painted in broad bands or spirals, and none is alike. The earliest modern lighthouses employed a catoptric light system that used parabolic silver mirrors to reflect lamplight into a concentrated beam. Often, this bowl- or cone-shaped reflector would be made to spin around the lamp, rotating the beam in the “searchlight” manner typical of many lighthouses. An everyday example of a catoptric light system can be found in a common household flashlight. In 1822 a revolutionary, multi-prismatic lens designed by Jean Augustin Fresnel ushered in the dioptric optical system for lighthouses, able to produce a five-times more powerful beam using the same light source as the catoptric system. Instead of reflecting the light, the Fresnel lens, which is actually a series of concentric rings of segmental lenses, refracted it. By 1860, every existing lighthouse in the United States had been converted to a Fresnel lens, and to fully take advantage of this more powerful light beam, lighthouses built after the lens’s introduction stood much taller than their predecessors. Later, an even more effective optical system known as the catadioptric system was developed, which was a hybrid of the two earlier systems. By 1900 most lighthouses began to convert to electricity and use incandescent bulbs; prior to that, lanterns fueled by wood, coal, or oil served as a lighthouse’s source light for the optical system.
The patterns of light beams emitted from these three different systems are as varied and individual as day marker patterns. Each lighthouse has its own characteristic intervals of light and eclipse. These intervals, known as night marks or signatures, are set in specific patterns defined with such names as flashing, occulting, group flashing, or group occulting. Beacons that are characterized as “flashing” have intervals of darkness that are longer in duration than the intervals of light; “occulting” lights display the opposite of this pattern. “Group flashing” or “group occulting” light patterns are simple groups of small flashes or eclipses. Obviously, there is no flash-eclipse pattern to a steady, uninterrupted “fixed” light, but rare patterns known as fixed flashing do exist; in such patterns, the beacon’s light fluctuates between a higher and lower beam intensity. What distinguishes each lighthouse is the rate of repetition for the intervals of flash and eclipse or fixed flashing. This unique repetition rate is called a period, and each lighthouse’s period is charted in United States Coast Guard publications known as light lists. In addition to a lighthouse’s night marks, its daymarks are included in these charts as well. Smart sailors still value these charts because they know that long after their fragile radios and radar rust into uselessness, the stalwart lighthouses will still be standing tall.
Light has been used as a beacon to mariners for thousands of years, for as long as man has taken to the sea. From the first primitive light beacons evolved the modern lighthouse, found on almost every waterway and coast in the world. To the uneducated eye each of these lighthouses, despite their distinct locations, seem to be irrelevant variations on a homogeneous design. However, nothing could be further from the truth; from height to lenses, each lighthouse is as unique as the landscape that surrounds it.
There is not one feature of a lighthouse that is arbitrary. By day, the varying color patterns painted on lighthouses help sailors distinguish their location along the coastline. These patterns, known as “daymarks,” are usually a combination of white, black, or red, can be painted in broad bands or spirals, and none is alike. The earliest modern lighthouses employed a catoptric light system that used parabolic silver mirrors to reflect lamplight into a concentrated beam. Often, this bowl- or cone-shaped reflector would be made to spin around the lamp, rotating the beam in the “searchlight” manner typical of many lighthouses. An everyday example of a catoptric light system can be found in a common household flashlight. In 1822 a revolutionary, multi-prismatic lens designed by Jean Augustin Fresnel ushered in the dioptric optical system for lighthouses, able to produce a five-times more powerful beam using the same light source as the catoptric system. Instead of reflecting the light, the Fresnel lens, which is actually a series of concentric rings of segmental lenses, refracted it. By 1860, every existing lighthouse in the United States had been converted to a Fresnel lens, and to fully take advantage of this more powerful light beam, lighthouses built after the lens’s introduction stood much taller than their predecessors. Later, an even more effective optical system known as the catadioptric system was developed, which was a hybrid of the two earlier systems. By 1900 most lighthouses began to convert to electricity and use incandescent bulbs; prior to that, lanterns fueled by wood, coal, or oil served as a lighthouse’s source light for the optical system.
The patterns of light beams emitted from these three different systems are as varied and individual as day marker patterns. Each lighthouse has its own characteristic intervals of light and eclipse. These intervals, known as night marks or signatures, are set in specific patterns defined with such names as flashing, occulting, group flashing, or group occulting. Beacons that are characterized as “flashing” have intervals of darkness that are longer in duration than the intervals of light; “occulting” lights display the opposite of this pattern. “Group flashing” or “group occulting” light patterns are simple groups of small flashes or eclipses. Obviously, there is no flash-eclipse pattern to a steady, uninterrupted “fixed” light, but rare patterns known as fixed flashing do exist; in such patterns, the beacon’s light fluctuates between a higher and lower beam intensity. What distinguishes each lighthouse is the rate of repetition for the intervals of flash and eclipse or fixed flashing. This unique repetition rate is called a period, and each lighthouse’s period is charted in United States Coast Guard publications known as light lists. In addition to a lighthouse’s night marks, its daymarks are included in these charts as well. Smart sailors still value these charts because they know that long after their fragile radios and radar rust into uselessness, the stalwart lighthouses will still be standing tall.
1. The author’s primary purpose is to (3)
- 1. relate a charming tale
- 2. detail the specific functions of a lighthouse
- 3. illustrate a point made by the author
- 4. offer an unbiased opinion
- 5. enumerate lighthouse facts
2. Based on the passage, which of the following is probably NOT true of lighthouses? (4)
- 1. The earliest lighthouses were bonfires built on the shore to guide fishermen back to the beach.
- 2. Up until very recently, the capturing and defending of lighthouses was often of strategic naval importance during a war.
- 3. The invention of the incandescent bulb lessened the duties of a lighthouse keeper.
- 4. A lighthouse’s “period” is randomly assigned from a list.
- 5. The tallest standing lighthouse has a catadioptric light system.
3. Based on information from the passage, a pattern defined as “group fixed occulting” would consist of (5)
- 1. a group of small fluctuations in light intensity
- 2. a group of small intervals of darkness that last longer than the intervals of light
- 3. a group of small intervals of light that last longer than the intervals of darkness
- 4. a group of small intervals of light and darkness that are equal in duration
- 5. This pattern is not possible.
4. In the passage, homogenous most closely means (2)
- 1. different
- 2. uniform
- 3. sturdy
- 4. colorful
- 5. antiquated
5. According to the passage, which of the following statements is/are true of catoptric light systems?
I. They were installed in lighthouses built prior to the 1820s.
II. They use refraction to create a concentrated light beam.
III. Only a few remain in American lighthouses today. (1)
I. They were installed in lighthouses built prior to the 1820s.
II. They use refraction to create a concentrated light beam.
III. Only a few remain in American lighthouses today. (1)
- 1. I only
- 2. III only
- 3. I and II only
- 4. I and III only
- 5. I, II, and III
