A. POSITION B. SPACE C. SPOT D. PLACE READ THE FOLLOWING PASSAGE A...

Question

65.

A. position

B. space

C. spot

D. place

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the

correct word for each of the blanks

The word laser was coined as an acronym for Light Amplification by the Stimulation 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 any outside intervention. Stimulated emission

is different because it occurs when an atom 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 physicists began trying to make stimulated emission dominate.

They sought ways by which one atom or molecule could stimulate many other to emit light, amplifying it

try 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 longer wavelength, 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.

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 ideas to a scientific journal.

Physical Review Letters, but Gould filed patent

application. Three decades latter, people still argue about who deserves the credit for the concept of the

laser.