Is an example for practicing the reading exam of the TOEFL, but you can use this for preparing your Cambridge exam. There are multiple examples of reading exams in this document.
The word laser was coined as an acronym for Light Amplification by the Stimulated
Emission of Radiation. Ordinary light, from the Sun or a light bulb, is emitted
spontaneously, when atoms or molecules get rid of excess energy by themselves, without
Line any outside intervention. Stimulated emission is different because it occurs when an atom
(5) or molecule holding onto excess energy has been stimulated to emit it as light.
Albert Einstein was the first to suggest the existence of stimulated emission in a paper
published in 1917. However, for many years physicists thought that atoms and molecules
always were much more likely to emit light spontaneously and that stimulated emission
thus always would be much weaker. It was not until after the Second World War that
(10) physicists began trying to make stimulated emission dominate. They sought ways by which
one atom or molecule could stimulate many others to emit light, amplifying it to much
higher powers.
The first to succeed was Charles H. Townes, then at Columbia University in New York.
Instead of working with light, however, he worked with microwaves, which have a much
(15) longer wavelength, and built a device he called a “maser,” for Microwave Amplification by
the Stimulated Emission of Radiation. Although he thought of the key idea in 1951, the first
maser was not completed until a couple of years later. Before long, many other physicists
were building masers and trying to discover how to produce stimulated emission at even
shorter wavelengths.
(20) The key concepts emerged about 1957. Townes and Arthur Schawlow, then at Bell
Telephone Laboratories, wrote a long paper outlining the conditions needed to amplify
stimulated emission of visible light waves. At about the same time, similar ideas
crystallized in the mind of Gordon Gould, then a 37-year-old graduate student at Columbia,
who wrote them down in a series of notebooks. Townes and Schawlow published their
(25) ideas in a scientific journal, physical Review Letters, but Gould filed a patent application.
Three decades later, people still argue about who deserves the credit for the concept of
the laser.
1. The word “coined” in line 1 could best be 2. The word “intervention” in line 4 can best
replaced by be replaced by
(A) created (A) need
(B) mentioned (B) device
(C) understood (C) influence
(D) discovered (D) source
, 3. The word “it” in line 5 refers to 7. In approximately what year was the first
(A) light bulb maser built?
(B) energy (A) 1917
(C) molecule (B) 1951
(D) atom (C) 1953
(D) 1957
4. Which of the following statements best
describes a laser? 8. The word “emerged” in line 20 is closest
(A) A device for stimulating atoms and in meaning to
molecules to emit light (A) increased
(B) An atom in a high-energy state (B) concluded
(C) A technique for destroying atoms or (C) succeeded
molecules (D) appeared
(D) An instrument for measuring light
waves
9. The word “outlining” in line 21 is closest in
meaning to
5. Why was Towne's early work with (A) assigning
stimulated emission done with (B) studying
microwaves? (C) checking
(A) He was not concerned with light (D) summarizing
amplification.
(B) It was easier to work with longer
wavelengths. 10. Why do people still argue about who
(C) His partner Schawlow had already deserves the credit for the concept of the
begun work on the laser. laser?
(D) The laser had already been (A) The researchers' notebooks were
developed. lost.
(B) Several people were developing the
idea at the same time.
6. In his research at Columbia University, (C) No one claimed credit for the
Charles Townes worked with all of the development until recently.
following EXCEPT (D) The work is still incomplete.
(A) stimulated emission
(B) microwaves
(C) light amplification
(D) a maser
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller gamepablo042. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.44. You're not tied to anything after your purchase.
