This set of Manufacturing Processes Multiple Choice Questions & Answers (MCQs) focuses on “Laser Beam Machining – 1”.
1. Mechanism of material removal in Laser Beam Machining is due to _____
a) mechanical erosion due to impact of high of energy photons
b) electro-chemical etching
c) melting and vaporisation due to thermal effect of impingement of high energy laser beam
d) fatigue failure
View Answer
Explanation: Laser beam machining is carried out utilizing the energy of coherent photons or laser beam, which is mostly converted into thermal energy upon interaction with most of the materials.
2. Laser Beam is produced due to _____
a) spontaneous emission
b) stimulated emission followed by spontaneous emission
c) spontaneous emission followed by Spontaneous absorption
d) spontaneous absorption leading to “population inversion” and followed by stimulated emission
View Answer
Explanation: Lasing process describes the basic operation of laser, i.e. generation of a coherent (both temporal and spatial) beam of light by “light amplification” using “stimulated emission”.
3. Which of the following processes does not use lasers?
a) Cladding
b) Alloying
c) Nitriding
d) Cutting
View Answer
Explanation: Laser Beam Machining or more broadly laser material processing deals with machining and material processing like heat treatment, alloying, cladding, sheet metal bending, etc.
4. Lasers are also used for_____
a) riveting
b) nitriding
c) rapid prototyping
d) facing
View Answer
Explanation: Nowadays, laser is also finding application in regenerative machining or rapid prototyping as in processes like stereo-lithography, selective laser sintering etc.
5. Laser stands for light amplification by stimulated emission of radiation.
a) True
b) False
View Answer
Explanation: Laser stands for light amplification by stimulated emission of radiation. The underline working principle of a laser was first put forward by Albert Einstein in 1917 through the first industrial laser for experimentation was developed around the 1960s.
6. Laser beams can have power density upto _____
a) 1 kW/mm2
b) 10 kW/mm2
c) 1 MW/mm2
d) 10 MW/mm2
View Answer
Explanation: Laser beam can very easily be focused using optical lenses as their wavelength ranges from half micron to around 70 microns. Focussed laser beam as indicated earlier can have power density in excess of 1 MW/mm2.
7. Laser causes a rapid substantial rise in _____ of the material.
a) local temperature
b) local pressure
c) indentation
d) cracks
View Answer
Explanation: As laser interacts with the material, the energy of the photon is absorbed by the work material leading to rapid substantial rise in local temperature. This in turn results in melting and vaporisation of the work material and finally material removal.
8. At _____ temperature an atom is considered to be at ground level.
a) absolute zero
b) 0oC
c) 100oC
d) 100 K
View Answer
Explanation: Each of the orbital electrons is associated with unique energy levels. At absolute zero temperature an atom is considered to be at ground level when all the electrons occupy their respective lowest potential energy.
9. The electrons at ground state can be excited to a higher state of energy by _____
a) increasing the pressure
b) lowering the energy
c) absorbing the energy
d) oxidising the atom
View Answer
Explanation: The electrons at ground state can be excited to higher state of energy by absorbing energy form external sources like increase in electronic vibration at elevated temperature, through chemical reaction as well as via absorbing the energy of the photon.
10. The geometry and radii of orbital paths of electrons depend on the presence of an electromagnetic field.
a) True
b) False
View Answer
Explanation: In the model of an atom, negatively charged electrons rotate around the positively charged nucleus in some specified orbital paths. The geometry and radii of such orbital paths depend on a variety of parameters like number of electrons, presence of neighbouring atoms and their electron structure, presence of an electromagnetic field, etc.
Sanfoundry Global Education & Learning Series – Manufacturing Processes.
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