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Doppler Effect
Have you ever wondered why the whistle of a traveling, distant locomotive predicts its approach several yards before anyone actually sees it? Or why an oncoming ambulanceÄ€™s screaming siren is heard momentarily several feet before the ambulance comes into full view, before it passes you, and why its siren is still heard faintly well after the ambulance is out of sight?
What you are witnessing is a scientific phenomenon known as the Doppler Effect. What takes place is truly remarkable. In both of these instances, when the train or ambulance moves toward the sound waves in front of it, the sound waves are pulled closer together and have a higher frequency. In either instance, the listener positioned in front of the moving object hears a higher pitch. The ambulance and locomotive are progressively moving away from the sound waves behind them, causing the waves to be farther apart and to have a lower frequency. These fast-approaching modes of transportation distance themselves past the listener, who hears a lower pitch.
Which sound waves have a higher pitch?
- A. Sound waves that are closer together
- B. Sound waves that are farther apart
- C. Sound waves that travel a long distance
- D. Sound waves that travel a short distance
Correct Answer: A
Rationale: The correct answer is A: Sound waves that are closer together. The Doppler Effect explains that when a source of sound is moving towards an observer, the sound waves are compressed, resulting in a higher frequency and thus a higher pitch. This phenomenon occurs when the source of the sound moves closer, causing the waves to be closer together. As the object moves away, the waves stretch out, leading to a lower frequency and a lower pitch. Therefore, sound waves that are closer together have a higher pitch, while those that are farther apart have a lower pitch.
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People of Hispanic origin were on the North American continent centuries before settlers arrived
from Europe in the early 1600s and the thirteen colonies joined together to form the United
States in the late 1700s. The first census of the new nation was conducted in 1790, and counted about four million people, most of whom were white. Of the white citizens, more than 80%
traced their ancestry back to England. There were close to 700,000 slaves and about 60,000 "free Negroes". Only a few Native American Indians who paid taxes were included in the census count, but the total Native American population was probably about one million. By 1815, the population of the United States was 8.4 million. Over the next 100 years, the
country took in about 35 million immigrants, with the greatest numbers coming in the late 1800s and early 1900s. In 1882, 40,000 Chinese arrived, and between 1900 and 1907, there were more
than 30,000 Japanese immigrants. But by far, the largest numbers of the new immigrants were
from central, eastern, and southern Europe. An enormous amount of racial and ethnic assimilation has taken place in the United States. In 1908, play-write Israel Zangwill first used the term "melting pot" to describe the concept of a place where many races melted in a crucible and re-formed to populate a new land. Some years during the first two decades of the 20th century, there were as many as one million new
immigrants per year, an astonishing 1 percent of the total population of the United States.
In 1921, however, the country began to limit immigration, and the Immigration Act of 1924
virtually closed the door. The total number of immigrants admitted per year dropped from as many as a million to only 150,000. A quota system was established that specified the number of
immigrants that could come from each country. It heavily favored immigrants from northern and western Europe and severely limited everyone else. This system remained in effect until 1965, although after World War II, several exceptions were made to the quota system to allow in
groups of refugees.
Why did the author write the passage?
- A. to outline the ways immigration has been restricted
- B. to emphasize the impact of migrants from Europe
- C. to explain and give examples of the concept of a 'melting pot'
- D. to summarize the main features of immigration
Correct Answer: D
Rationale: The correct answer is D because the passage provides a comprehensive overview of the history of immigration in the United States. It covers various aspects such as the origins of different ethnic groups, the influx of immigrants from Europe and Asia, the term 'melting pot,' and the evolution of immigration policies over time. The passage summarizes key features of immigration, including population numbers, demographic groups, major immigrant waves, and changes in immigration laws. Therefore, the main purpose of the passage is to summarize the main features of immigration in the United States.
Have you ever wondered why the whistle of a traveling, distant locomotive predicts its approach several yards before anyone actually sees it? Or why an oncoming ambulance's screaming siren is heard momentarily several feet before the ambulance comes into full view, before it passes you, and why its siren is still heard faintly well after the ambulance is out of sight?
What you are witnessing is a scientific phenomenon known as the Doppler Effect. What takes place is truly remarkable. In both of these instances, when the train or ambulance moves toward the sound waves in front of it, the sound waves are pulled closer together and have a higher frequency. In either instance, the listener positioned in front of the moving object hears a higher pitch. The ambulance and locomotive are progressively moving away from the sound waves behind them, causing the waves to be farther apart and to have a lower frequency. These fast-approaching modes of transportation distance themselves past the listener, who hears a lower pitch.
What is the main idea of the passage?
- A. Trains and ambulances produce specific sounds
- B. Low-frequency waves produce high-pitched sounds.
- C. High-frequency waves produce low-pitched sounds.
- D. The Doppler Effect explains why sound is heard more strongly initially and then faintly after a moving object has passed.
Correct Answer: D
Rationale: The main idea of the passage is to explain the phenomenon known as the Doppler Effect, which describes how the frequency of sound waves changes as a source of sound moves relative to an observer. The passage illustrates this with examples of a traveling train and ambulance. As the objects approach the listener, the sound waves are compressed, resulting in a higher frequency and a higher pitch heard by the observer. Conversely, as the objects move away, the sound waves are stretched, leading to a lower frequency and a lower pitch. Therefore, the correct answer is D, as it summarizes the key concept of the Doppler Effect and its impact on sound perception.
For what type of writing was Mr. Asimov most famous for?
For what type of writing was Mr. Asimov most famous?
- A. Juvenile fiction
- B. Mystery
- C. Popular science
- D. Science fiction writing
Correct Answer: D
Rationale: Mr. Asimov was most famous for his works in science fiction writing. He was a prolific writer in this genre, known for his influential and groundbreaking contributions to science fiction literature. Asimov's works often explored scientific concepts and imagined futuristic scenarios, solidifying his legacy as one of the most renowned science fiction authors.
Homophones
English is a vibrant, changing, dynamic language. It allows people to express their thoughts in diverse ways, as there are many synonyms and antonyms to choose from. The hardest part for the English speaker - or those learning English as a second language - is learning about homonyms. These are words that sound alike but are spelled different ways, with different meanings.
One example is "One". This word, spelled "one" means the numeral 1, an amount. If spelled "won," it means to be victorious. No wonder spelling is a difficult skill to master! Other homonyms encountered by the beginning English speaker are "to, two, too," "four, for, fore," "there, their, they're" and "son, sun" to name just a few. This is one reason that "Spell check" programs on word processing computers cannot be completely accurate, because the way a word is spelled depends on the context of the sentence. Proofreaders will always be in demand.
What inference can be drawn from the article?
- A. English is an easy language to learn.
- B. English grammar rules are universal and straightforward.
- C. English is a difficult language to master.
- D. English vocabulary is consistent and predictable.
Correct Answer: C
Rationale: The correct inference that can be drawn from the article is that English is a difficult language to master. The article discusses the challenges English speakers and learners face with homonyms, words that sound alike but are spelled differently with different meanings. It emphasizes the complexity of mastering English spelling and the presence of homonyms like 'one' and 'won,' 'to, two, too,' 'four, for, fore,' 'there, their, they're,' and 'son, sun.' This complexity is highlighted as a reason why spelling can be challenging to master, leading to the conclusion that English is a difficult language to learn and master.
The Summer Olympic Games. Once every four years the countries of the world send their best and brightest to participate in the Summer Olympic Games. The site for the event is decided years before, and most countries contend strongly for the privilege to host the Games. The 2008 games were held in Bejing, China.
There is a lot of pageantry and tradition attached to the event. The opening ceremony is elaborate and awe-inspiring. China put on a spectacularly beautiful fireworks display to welcome the world's athletes in 2008.
The track events, water events (swimming, diving) and precision activities such as archery and rhythmic gymnastics are wonderful to watch. Seeing these athletes perform their special skills is a treat for those of us who achieve a vicarious satisfaction from it. Everyone roots for the athletes from their own country and we thrill when our anther is played during the medal ceremony. Being an Olympian is an honor every athlete dreams of.
How often are the Summer Olympic Games held?
- A. Every two years.
- B. Every four years.
- C. Annually.
- D. Once a decade.
Correct Answer: B
Rationale: The Summer Olympic Games are held 'once every four years,' as stated in the text. This timeframe allows countries to send their best athletes to participate. The correct answer is B, 'Every four years,' making it a significant and eagerly anticipated global event. The four-year interval also allows for ample time for countries to prepare, build excitement, and showcase their best talents on a world stage.