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 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.
Which sound waves have a lower 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: B
Rationale: Sound waves that are farther apart have a lower pitch. In the Doppler Effect, as a source of sound moves away from a listener, the sound waves get stretched out, causing a decrease in frequency and resulting in a lower pitch. Conversely, when a source of sound moves toward a listener, the sound waves get compressed, leading to an increase in frequency and a higher pitch. This phenomenon explains why the pitch of sound changes depending on whether the source is moving towards or away from the listener.
You may also like to solve these questions
Croatian-born inventor Nikola Tesla is often called the "forgotten scientist". Although he
invented the alternating current (AC) motor and developed an AC electricity generation system, he never received historical credit for many of his achievements, unlike one of his first employer and eventual nemesis, inventor Thomas Edison
Tesla made the first sketches of his idea for a brushless of his idea for a brushless AC motor while he was a student at the University of Prague in 1882. His interest in electricity generation led him to Paris where he was employed by the Continental Edison Company later that year to repair Edison's direct current (DC) power plants. Two years later, Tesla immigrated to New York City and acquired a job as an engineer at
Thomas Edison's headquarters in Manhattan. Edison was impressed with Tesla's work ethic and
ingenuity. He challenged the young scientist to develop an improved design for his DC
generators for $50,000. Tesla experimented for months, finally presenting Edison with the
solution he needed. Edison reneged on the deal, telling Tesla that he didn't understand American humor. Tesla soon left Edison in order to begin his own electric light company
Tesla filed and was granted more than 30 patents for his inventions in 1887 and 1888. He soon
had financial backing for his ideas from one of Edison' main competitors, Westinghouse. In the
1890's Tesla experimented with x-rays, developed a high-voltage electrical transformer call the
Tesla coil, and demonstrated the propagation of radio waves two years before the "Father of
Radio" Guglielmo Marconi. He was also the first to harness the mammoth potential energy of
Niagara Falls. He worked with General Electric to install AC generators with turbines driven by the falling waters of the Niagara River, creating the first modern power plant although a brilliant scientist, Tesla was not an astute businessman. He created his own obscurity by relinquishing
royalty rights for his inventions to major corporations for the purpose of raising funds for future projects.
What did Tesla accomplish while attending the University of Prague?
- A. Improved the design for Edison's DC generators.
- B. Made repairs to Edison's direct current power plants.
- C. Made designs for a brushless alternating current motor.
- D. Developed a high-voltage electrical transformer.
Correct Answer: C
Rationale: While attending the University of Prague, Tesla made designs for a brushless alternating current motor. This innovation marked the beginning of his groundbreaking work in the field of electricity and laid the foundation for his future achievements. Tesla's early sketches and ideas for the AC motor at the University of Prague set him on a path that would ultimately revolutionize the way electricity was generated and utilized.
The immune system is a network of cells, tissues, and organs that defends the body against attacks by foreign invaders. These invaders are primarily microbes—tiny organisms such as bacteria, parasites, and fungi— that can cause infections. Viruses also cause infections, but are too primitive to be classified as living organisms. The human body provides an ideal environment for many microbes. It is the immune system’s job to keep the microbes out or destroy them. The immune system is amazingly complex. It can recognize and remember millions of different enemies, and it can secrete fluids and cells to wipe out nearly all of them. The secret to its success is an elaborate and dynamic communications network. Millions of cells, organized into sets and subsets, gather and transfer information in response to an infection. Once immune cells receive the alarm, they produce powerful chemicals that help to regulate their own growth and behavior, enlist other immune cells, and direct the new recruits to trouble spots. Although scientists have learned much about the immune system, they continue to puzzle over how the body destroys invading microbes, infected cells, and tumors without harming healthy tissues. New technologies for identifying individual immune cells are now allowing scientists to determine quickly which targets are triggering an immune response. Improvements in microscopy are permitting the first-ever observations of living B cells, T cells, and other cells as they interact within lymph nodes and other body tissues. In addition, scientists are rapidly unraveling the genetic blueprints that direct the human immune response, as well as those that dictate the biology of bacteria, viruses, and parasites. The combination of new technology with expanded genetic information will no doubt reveal even more about how the body protects itself from disease.
What is the author's primary purpose in writing the essay?
- A. to persuade
- B. to analyze
- C. to inform
- D. to entertain
Correct Answer: C
Rationale: The correct answer is 'C: to inform.' The essay provides detailed information about the immune system, its functions, complexities, and the ongoing research in the field. The author's main goal is to educate and increase the reader's understanding of how the immune system works and its significance in protecting the body from diseases. There is no attempt to persuade, analyze for evaluation, or entertain the audience; instead, the focus is on imparting knowledge and insights about the immune system.
Subjective exams measure your ability in several areas. Besides recall information, you must be
able to realize content logically and intelligently express yourself in a clearly understood manner. Subjective test provide opportunity for students to show their broad knowledge of a subjective
area. Answers may be in the form of paragraphs or lengthy essays. When your review for an essay exam, concentrate on main ideas rather than details. Since essay tests are less to a few questions, they are likely to deal with more important ideas of a subject. Prepare a list of question you think might be asked. Write an answer to each of your questions. Rather than writing complete sentence down your thoughts in outline form. Doing so will help
you organize the information so that you can express yourself clearly.
When you take the test, read through all the questions before you start to write. Allot time for each question, spending more time for questions worth the most points. Read each question carefully to determine exactly what they are asked. Pay attention to words such as define, illustrate, explain, list, compare, and contrast. Each work requires a different type of response. Write a brief outline of your answer on scrap paper or the back of the test. Make sure you include all the important ideas that are within the limits of the question. In other words, do not write more than is asked for each answer. When you write your answer, keep it specific and as brief as possible. In the introductory sentence it is often helpful to make a general statement that includes
important points addressed in each question. Such a topic sentence serves as a framework for your answer. Then use your outline to develop the main point and subtopics. Add substance to
your answer by including as many facts as possible to support your answer.
Check your paper before you submit it. Look for mistakes in grammar, spelling, sentence
structure, and punctuation. Unless you are certain an answer is wrong, do not change it. Your answer is an educated guess and is usually your best chance of answering correctly.
In the above passage, the word 'subjective' refers to test questions that:
- A. Allow you to choose an answer
- B. Are matching
- C. Are true or false
- D. Require you to write your own answer
Correct Answer: D
Rationale: The term 'subjective' in the passage refers to test questions that require you to write your own answer, as mentioned in the text. Subjective tests typically involve expressing your understanding and knowledge in your own words, often through paragraphs or essays. This type of assessment allows students to demonstrate their comprehension and analytical skills by formulating responses based on their interpretation of the content, rather than selecting from predefined options. Therefore, the correct answer is D: 'Require you to write your own answer.'
Lightning Strikes
The old wives' tale of "Lightning never strikes twice" has been proven untrue time and time again. Lightning forms from negative and positive charges within clouds and from the earth below. When these charges react with each other, the air between the cloud and the earth ionizes, which produces a lightning flash. Lightning is actually a series of multiple events consisting of a leader stroke of lightning, followed by as many as 40 smaller strokes of lightning. Being just split seconds apart, these strokes of lightning often reflect off the lining of the clouds.
Lightning rods that extend from above the roof to the ground protect buildings by forming a low resistance path for the lightning so that the lightning does not enter the building, but rather defuses as it penetrates the ground.
Some myths about lightning need to be explained. Lightning does strike tall buildings often, and during a particularly violent storm, a tall building may be hit by lightning several times. The safest place during a thunder and lightning storm is in a metal car or lying flat, face down, in the open, not under a tree as the myth suggests.
Many people believe that thunder and lightning are connected; however, this proves to be true only about 50% of the time, so if you're waiting for the clap of thunder, you're missing out on some exciting strokes of lightning!
Lightning causes injuries, deaths, and forest fires each year. However, some scientists reveal the positive aspects of lightning because it releases nitrogen into the atmosphere which the raindrops then deliver to earth to fertilize our soil.
What does the word 'penetrates' mean?
- A. To shield
- B. To pierce
- C. To cover
- D. To obscure
Correct Answer: B
Rationale: The word 'penetrates' means 'to pierce'. In the context provided, it refers to lightning diffusing into the ground by breaking through a surface. The sentence '...defuses as it penetrates the ground' indicates that the lightning breaks through the ground rather than shielding, covering, or obscuring it.
Considered the most influential architect of his time, Frank Lloyd Wright (1867-1959) was born in the small rural community of Richland Center, Wisconsin. He entered the University of
Wisconsin at the age of 15 as a special student, studying engineering because the school had no course in architecture. At the age of 20 he then went to work as a draughtsman in Chicago in order to learn the traditional, classical language of architecture. After marrying into a wealthy
business family at the age of 21, Wright set up house in an exclusive neighborhood in Chicago, and after a few years of working for a few architectural firms, set up his own architectural office. For twenty years he brought up a family of six children upstairs and ran a thriving architectural
practice of twelve or so draughts men downstairs. Here, in an idyllic American suburb, with
giant oaks, sprawling lawns, and no fences, Wright built some sixty rambling homes by the year 1900. He became the leader of a style known as the "Prairie" school - houses with low-pitched roofs and extended lines that blended into the landscape and typified his style of "organic
architecture".
By the age of forty-one, in 1908, Wright had achieved extraordinary social and professional success. He gave countless lectures at major universities and started his Taliesin Fellowship - a visionary social workshop. In 1938 he appeared on the cover of Time magazine, and later, on a
two-cent stamp. The most spectacular buildings of his mature period were based on forms borrowed from nature, and the intentions were clearly romantic, poetic, and intensely personal. Examples of these buildings are Tokyo's Imperial Hotel (1915-22: demolished 1968), and New
York City's Guggenheim Museum (completed 1959). He continued working until his death in 1959, at the age of 92, although in his later years, he spent as much time giving interviews and
being a celebrity, as he did in designing buildings. Wright can be considered an essentially
idiosyncratic architect whose influence was immense but whose pupils were few.
What is the main focus of the passage?
- A. the development of modern architecture in America
- B. the contributions of the 'Prairie' School to modern architecture
- C. the life and achievements of a famous architect
- D. the influence of the style of 'organic architecture' in America
Correct Answer: C
Rationale: The passage primarily focuses on the life and achievements of the famous architect Frank Lloyd Wright. It provides a detailed account of Wright's early life, education, architectural influences, personal life, professional success, and notable projects. The passage highlights key events in Wright's life, from his education and early work experiences to his architectural style, social impact, and recognition in the architectural world. While elements of modern architecture, the 'Prairie' School, and 'organic architecture' are mentioned, they serve as supporting details to illuminate various aspects of Wright's life and career. Therefore, the correct answer is 'C: the life and achievements of a famous architect.'
Nokea