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BEST IELTS Academic Reading Test 525
IELTS ACADEMIC READING TEST 525 – PASSAGE – 1
IELTS ACADEMIC READING TEST – 525
READING PASSAGE – 1
Biology of Light
A. The phenomena of light has always been pondered and mythologized about, but only until recently has there been systematic efforts to determine its basic properties and nature. A whole host of cultures have their own take on the origin of light or the day/night cycle. Some stories see the light and dark duality as a great cosmic struggle. In the Norse mythology of Scandinavia, wolves chase both the moon and sun as they arch across the sky.
Scientific inquiry into light is yet another expression of our natural curiosity about the world. In the West, there have been postulations about light since the time of Ancient Greece. This line of questioning sometimes has lead to practical applications as well, allowing us to harness the properties of different kinds of light for the benefit of all.
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B. The Greek hills and islands produced many naturalists and mathematicians in ancient times. Several inquired about the nature of light. Euclid, famous for his work in geometry, theorized that light traveled in straight lines and studied the laws of reflection. Another different theorist prefigured the wave/particle debate over the nature of light by stating that it was made up of atoms that moved at infinite speed. The biggest advance in the nature of light during this time, though, was from an Islamic scientist named Al-Haitham.
He theorized that our vision was a result of light entering our eyes. Al-Haitham believed this light to be very, very fast but ultimately finite in speed. He also guessed correctly that the refraction effect was a result of light traveling at different speeds through different mediums. The camera obscura, or pinhole camera, that he invented would later help others understand human sight. Further advances into the biology of light would not be made for about 600 years, or until the beginning of the 17th century.
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C. Johannes Kepler was a great astronomer whose work was part of the revolution, in the Western world, from ancient ways of looking at nature to a more systematic and scientific way. Kepler’s work led to a greater understanding of the orbits of planets and laid the foundations for modern astronomy. He also studied the phenomena of light and made important formulations of it. The inverse square law was formulated by Kepler, which states that the intensity of light goes down proportionately by the square of the distance away from the source.
For example, if the distance from an object to a light source is doubled, the intensity of the light reaching the object is reduced to one-fourth of the previous intensity. If the distance is tripled, the intensity is reduced to one-ninth of the previous intensity, or three squared, and so forth. Kepler also theorized that the image of the world we receive onto our eyes is actually upside-down due to the light entering the eye, much like in the camera obscura invented by Al-Haitham. Oddly, Kepler did not expound upon the laws of refraction, and he also incorrectly assumed the speed of light to be infinite.
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D. Over the next centuries various other scientific greats added to our understanding of light. Isaac Newton’s Opticks was a seminal work in color and refraction. During his time, there was a debate over whether or not light was actually a particle or a wave. The true nature of light turned out to be more complicated, actually having properties of both, but at that time it was thought Newton made a mistake by pushing a particle theory of light.
E. The work of two more scientists, Michael Faraday and James Clerk Maxwell, created the modern understanding of light. Faraday’s experiments, data, and incipient theory on light allowed Maxwell to formulate a complete mathematical understanding of light in relation to electricity and magnetism. By realizing and explaining how these forces were unified, modern physicists could delve into the more counterintuitive and interesting properties of light.
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However, even Maxwell’s theories needed improvement since he assumed that all electromagnetic waves, including light, propagated through a substance that permeated all space. Since sound had to travel in a medium such as air or water, it was thought light needed such one as well. Later experiments disproved the notion of a ‘luminous aether’ as well as refining the measurements for the speed of light.
F. The leap from a classical view of light to a quantum view of light took place in the 20th century. Albert Einstein was responsible for two discoveries, which fundamentally altered the way the light was perceived. The first discovery, and the one for which he received a Nobel prize in physics, was his explanation of the photoelectric effect. Einstein noticed that if a certain type of light were shined onto a piece of reactive metal, it would emit electrons. If another type of light with a lower frequency, and therefore less energy, were used instead, the metal would not emit any electrons, regardless of the amount of that lower frequency light.
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Einstein used the earlier work of Max Planck to show how this particle-like behavior of light showed that its energy wasn’t continuous, but rather, came in ‘quanta.’ Light could only exist at certain energy levels and nowhere in between. Einstein also used Maxwell’s equations to develop his Special Theory of Relativity. Among many things, this theory states that light is a sort of universal speed limit and that nothing can travel faster than it.
G. Scientists today are continuing to try and understand properties of light. Useful technologies, such as fiber optics and laser communications, have already been developed. Future work may even give us computers that make calculations using photons instead of electrons. The long search for the deeper meaning of something around us all the time has been most useful and beneficial.
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QUESTIONS 1 – 8
Choose your answers from the box.
NB There are more words than spaces so you will not use them all.
You may use any of the words more than once.
OUR KNOWLEDGE OF LIGHT
In the Western World, there have been investigations into the … (1)… of light since the time of the Ancient … (2)…. They laid some of the foundations for … (3)… inquiry into light. People either… (4)… on what light was, or tried to describe very broad mathematical properties of it.
After the …(5)… Revolution in Europe, some …(6)… delved deeper and deeper into the intrinsic nature of light, including what it was made of, how it acted, and how fast it went. Recent … (7)… about light include some … (8)… and unintuitive findings.
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WORD LIST
| Religious | Speculated | Unknowable | Nature |
| Future | Created | Beneficial | Scientists |
| Past | Outcomes | Scandinavians | Nurture |
| Nobel | Discoveries | Undesirable | Adventurers |
| Pragmatic | Greeks | Scientific | Unexpected |
QUESTIONS 9 – 15
Look at the following notes that have been made about the matches described in Reading Passage 1. Decide which type of Match (A—H) corresponds with each description and write your answers for questions 9-15.
NB There are more matches than descriptions so you will not use them all. You may use any of the words more than once.
9. was the first to theorize that vision was light entering our eyes.
10. formulated how nothing in the universe could exceed the speed of light.
11. used a previous person’s work to determine light’s relationship with electromagnetism.
12. invented a special device that helped to understand our vision.
13. discovered properties about the strength of light as it leaves a source.
14. his work was used to determine how the energy in light is discrete.
15. early theorist who studied the reflection of light.
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Choice of Matches
A. Johannes Kepler
B. Max Planck
C. Isaac Newton
D. Al-Haitham
E. Albert Einstein
F. Michael Faraday
G. Euclid
H. James Clerk Maxwell
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IELTS Academic Reading Test
ANSWERS
1. NATURE
2. GREEKS
3. FUTURE
4. SPECULATED
5. SCIENTIFIC
6. SCIENTISTS
7. DISCOVERIES
8. UNEXPECTED
9. D
10. E
11. H
10. E
12. D
13. A
14. B
15. G
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