World Science and Technology – Exercise – 1

21. What was the active medium used in the first working laser ever constructed?

(a) A diamond block
(b) Helium-neon gas
(c) A ruby rod
(d) Carbon dioxide gas

Answer
Answer : (c)
Explanation
Explanation : Theodore Maiman built the first working laser using a ruby rod while working at Hughes Research Laboratories in Malibu, California. It lased for the first time on May 16, 1960. Let us discuss.
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22. What are three types of lasers?

(a) Gas, metal vapor, rock
(b) Pointer, diode, CD
(c) Diode, inverted, pointer
(d) Gas, solid state, diode

Answer
Answer : (d)
Explanation
Explanation : The first laser was a solid state laser. Solid state refers to any solid material like a glass rod. Diode lasers are very common because they are used to read compact disks and digital video disks in computers, CD players, and DVD players. Before diode lasers, the most common type of laser may have been the helium-neon laser, in which the active medium is a combination of the two gasses helium and neon. Let us discuss.
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23. Once the active medium is excited, the first photons of light are produced by which physical process?

(a) Blackbody radiation
(b) Spontaneous emission
(c) Synchrotron radiation
(d) Planck’s oscillation

Answer
Answer : (b)
Explanation
Explanation : Spontaneous emission is what you see with most “glow in the dark” toys. You excite the toy by exposing it to bright light, then the toy glows in the dark by spontaneously emitting photons as the excited atoms relax back down to their normal state. Let us discuss.
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24. The first step to getting output from a laser is to excite an active medium. What is this process called?

(a) Pumping
(b) Exciting
(c) Priming
(d) Raising

Answer
Answer : (a)
Explanation
Explanation : A collection of atoms or molecules that can be excited to a higher energy state is called an active medium. Before lasing can occur, the active media is “pumped”. The process of raising the atoms in the active media from a lower energy state to a higher state is like pumping water up from a well. Let us discuss.
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25. What does AM mean?

(a) Angelo marconi
(b) Anno median
(c) Amplitude modulation
(d) Amperes

Answer
Answer : (c)
Explanation
Explanation : Amplitude modulation was the first type to be used in radio. It works well with HF and morse code. Let us discuss.
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