With reference to Visible Light Communication (VLC) technology, which of the following statements are correct ? 1. VLC uses electromagnetic spectrum wavelengths 375 to 780 nm. 2. VLC is known as long-range optical wireless communication. 3. VLC can transmit large amounts of data faster than Bluetooth. 4. VLC has no electromagnetic interference. Select the correct answer using the code given below:
- A.1, 2 and 3 only
- B.1, 2 and 4 only
- C.1, 3 and 4 only
- D.2, 3 and 4 only
Correct answer
Explanation
The correct answer is C, 1, 3 and 4 only. VLC sends data with visible light, which is fast and free of radio interference, but it works only over short distances.
Visible Light Communication switches LED lights on and off millions of times a second, too fast for the eye to notice, and a photodetector reads these flickers as data. Li-Fi is its best-known form. It uses the visible band of roughly 375 to 780 nanometres, so statement 1 is correct. Because the visible spectrum is huge and unlicensed, VLC can move far more data than Bluetooth, so statement 3 is correct. It uses light, not radio waves, so it causes no electromagnetic interference and is suited to hospitals and aircraft, so statement 4 is correct.
Statement 2 is wrong: light cannot pass through walls and fades with distance, so VLC is short-range, not long-range.
So A, B and D, which include statement 2, are wrong.
Exam tip: VLC/Li-Fi = LED light, 375–780 nm, fast, no EM interference, short range, blocked by walls.
Practice Questions
View allIn the context of the developments in Bioinformatics, the term 'transcriptome', sometimes seen in the news, refers to
- A.a range of enzymes used in genome editing
- B.the full range of mRNA molecules expressed by an organism
- C.the description of the mechanism of gene expression
- D.a mechanism of genetic mutations taking place in cells
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The transcriptome is the complete set of RNA transcripts, chiefly messenger RNA, made from the genes at a given time.
Read the full explanation →Consider the following aircraft :
1. Rafale
2. MiG-29
3. Tejas MK-1
How many of the above are considered fifth generation fighter aircraft ?
- A.Only one
- B.Only two
- C.All three
- D.None
Show answer
Rafale, MiG-29 and Tejas Mk-1 are all fourth or 4.5 generation fighters; none of them is a fifth-generation aircraft. A fifth-generation fighter is defined by all-aspect stealth, internal weapons bays, supercruise and advanced sensor fusion.
Read the full explanation →With reference to "Blockchain Technology", consider the following statements :
1. It is a public ledger that everyone can inspect, but which no single user controls.
2. The structure and design of blockchain is such that all the data in it are about cryptocurrency only.
3. Applications that depend on basic features of blockchain can be developed without anybody's permission.
Which of the statements given above is/are correct?
- A.1 only
- B.1 and 2 only
- C.2 only
- D.1 and 3 only
Show answer
A blockchain is an open, shared ledger that no single party controls, and anyone can build on a public blockchain without asking permission.
Read the full explanation →In the context of recent advances in human reproductive technology, "Pronuclear Transfer" is used for
- A.fertilization of egg in vitro by the donor sperm
- B.genetic modification of sperm producing cells
- C.development of stem cells into functional embryos
- D.prevention of mitochondrial diseases in offspring
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Pronuclear transfer is a mitochondrial replacement technique that stops a mother from passing faulty mitochondria to her child. Mitochondria have their own small DNA, inherited only from the mother; defects in it cause serious muscle, heart and brain diseases.
Read the full explanation →It is possible to produce algae based biofuels, but what is/are the likely limitation(s) of developing countries in promoting this industry?
1. Production of algae based biofuels is possible in seas only and not on continents.
2. Setting up and engineering the algae based biofuel production requires high level of expertise/technology until the construction is completed.
3. Economically viable production necessitates the setting up of large scale facilities which may raise ecological and social concerns.
Select the correct answer using the code given below.
- A.1 and 2 only
- B.2 and 3 only
- C.3 only
- D.1, 2 and 3
Show answer
The real hurdles are the high technology needed to build algae plants and the very large scale they need to pay off; algae can be grown on land.
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