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Q5 (IAS/2016) Science & Technology › ICT, AI, Cybersecurity & Emerging Tech › Wireless communication technologies Official Key

With reference to 'LiFi', recently in the news, which of the following statements" is/are correct? 1. It uses light as the medium for high-speed data transmission. 2. It is a wireless technology and is several times faster than. 'WiFi'. Select the correct answer using the code given below.

Result
Your answer: —  ·  Correct: C
Explanation

The correct answer is option C because both statements about LiFi are correct.

LiFi is a wireless optical networking technology that uses light emitting diodes (LEDs) for transmission [1]of data. This confirms that Statement 1 is correct - LiFi uses light as the medium for data transmission. Li-Fi is a visible light communication technology useful to obtain high speed wireless communication.[2]

Regarding Statement 2, the documents clearly establish that LiFi is indeed wireless and significantly faster than WiFi. Li-Fi provides better bandwidth, efficiency, connectivity and security than Wi-Fi and has already achieved high speeds larger than 1 Gbps under the laboratory conditions.[3] Additionally, Li-Fi has achieved data transmission speeds of 10 Gbps and even 224 Gbps with room-scale coverage.[4] Since typical WiFi speeds are in the range of hundreds of Mbps, LiFi's speeds of several Gbps are indeed "several times faster" than WiFi, making Statement 2 correct as well.

Therefore, both statements 1 and 2 are correct, making option C the right answer.

Sources
  1. [1] https://www.tec.gov.in/pdf/Studypaper/lifi%20study%20paper%20-%20approved.pdf
  2. [2] https://www.tec.gov.in/pdf/Studypaper/lifi%20study%20paper%20-%20approved.pdf
  3. [3] https://www.tec.gov.in/pdf/Studypaper/lifi%20study%20paper%20-%20approved.pdf
  4. [4] https://en.wikipedia.org/wiki/Li-Fi
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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. With reference to 'LiFi', recently in the news, which of the following statements" is/are correct? 1. It uses light as the medium for hi…
At a glance
Origin: Books + Current Affairs Fairness: Low / Borderline fairness Books / CA: 3.3/10 · 3.3/10

This is a classic 'Emerging Tech' question derived directly from Science & Tech current affairs (2015-16 hype cycle). While static books explain the physics of light, they do not cover 'LiFi' specifically. The strategy is simple: if a new tech acronym appears in headlines promising to replace an old standard (WiFi), memorize its medium (Light vs Radio) and its primary advantage (Speed).

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Does LiFi use light (visible light or optical spectrum) as the medium for high-speed data transmission?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 15: Infrastructure > National Optical Fibre Network (NOFN) > p. 463
Presence: 5/5
“• The project envisages an optimal mix of optical fibre, radio and satellite media. ۰• The aim is to establish a highly scalable network infrastructure accessible on non-discriminatory basis, affordable broadband connectivity of 2 Mbps to 20 Mbps for all households. Till August 2019, 1.25 lakh GPs were already connected with high-speed broadband connectivity under BharatNet.”
Why this source?
  • Explicitly lists 'optical fibre' as one of the media used in a project to provide high‑speed broadband connectivity.
  • Links optical media to delivery of high‑speed broadband, showing light-based channels are used for data transmission in networks.
Science-Class VII . NCERT(Revised ed 2025) > Chapter 11: Light: Shadows and Reflections > Activity 11.1: Let us investigate > p. 156
Presence: 3/5
“Caution — Use a laser only under teachers' supervision. Avoid using high-power lasers for this activity; a low-power laser pointer is suffi cient. Never point the laser beam directly at anyone's eyes, as it can cause serious eye damage. Pass a laser beam through a beaker fi lled with water in which a drop of milk is added to make the laser beam easily visible. What do you observe? Do you see that the beam of laser light inside water follows a straight path? However, light can sometimes even bend around corners! This is something you will learn in the higher grades.”
Why this source?
  • Describes use of a laser beam (a directed form of light) in an experiment, showing light can be generated and guided as a beam.
  • Demonstrates that visible/laser light can travel in a controlled, directed path—an attribute used in light‑based data links.
Statement 2
Is LiFi a wireless communication technology?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 5/5
"a wireless optical networking technology that uses light emitting diodes (LEDs) for transmission of data."
Why this source?
  • Explicitly describes Li‑Fi as "a wireless optical networking technology".
  • Defines the term as visible light communication (VLC) using light as the medium, similar to Wi‑Fi.
Web source
Presence: 5/5
"Li‑Fi is a visible light communication technology useful to obtain high speed wireless communication."
Why this source?
  • States that "Both Wi‑Fi and Li‑Fi can provide wireless Internet access to users."
  • Specifies Li‑Fi is a visible light communication technology for high speed wireless communication, contrasting Wi‑Fi's radio waves.
Web source
Presence: 5/5
"a fascinating optical wireless communication technology – Li‑Fi Technology."
Why this source?
  • Describes Li‑Fi as an "optical wireless communication technology."
  • Places Li‑Fi at the forefront of Internet-of-Things connectivity using light for data transmission.

Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 15: Infrastructure > TELECOM SECTOR > p. 462
Strength: 4/5
“• Indian telecom network is second largest in the world in terms of telephone connections (after China). • The mobile industry contributes around 6. 5 per cent to the country's GDP. • As per the 2019-20 annual report of the Department of Telecommunications, GOI: a • India has over 118 crore telephone connections, out of which over 115 crore are wireless telephone connections. • Share of wireless telephones in total telephones is more than 98 per cent.”
Why relevant

States that over 98% of telephone connections are wireless, showing 'wireless' is a major category of telecommunication distinct from wired services.

How to extend

A student could take the rule that communications can be classed as wired vs wireless and then check whether LiFi transmits without physical wires (using light) to place it in the wireless category.

Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 12: Transport, Communications and Trade > Radio, Television, and Cinema > p. 44
Strength: 5/5
“Radio, television and cinema (films) are the electronic media of mass communication, unlike postal, telegraphic, telephone, and telex services which are essentially of personal nature. Unlike telephone, radio is a means of wireless communication. It is a very powerful medium to transmit and receive useful information, news and variety of entertainment programmes including sports. The All India Radio came to be known as 'Akashvani' from 1957. At the time of Independence, there were six radio (Akashwani) stations. At preset All India Radio is accessible to almost 98.5% of the total population of the country. Prasar Bharati (Broadcasting Corporation of India) is the public service broadcaster in the country.”
Why relevant

Defines radio as a means of wireless communication, establishing that electromagnetic media (radio waves) are examples of wireless transmission.

How to extend

Knowing radio uses electromagnetic waves through the air, a student could compare this to light (also an electromagnetic wave) and infer that light-based data links may likewise be considered wireless.

FUNDAMENTALS OF HUMAN GEOGRAPHY, CLASS XII (NCERT 2025 ed.) > Chapter 7: Transport and Communication > Satellite Communication > p. 68
Strength: 4/5
“Today Internet is the largest electronic network on the planet connecting about 1,000 million people in more than 100 countries. Satellites touch human lives in many ways. Every time you use a cell phone to call a friend, send an SMS or watch a popular programme on cable television. You are using satellite communication. Communication through satellites emerged as a new area in communication technology since the 1970s after U.S.A. and former U.S.S.R. pioneered space research. Artificial satellites, now, are successfully deployed in the earth's orbit to connect even the remote corners of the globe with limited onsite verification. These have rendered the unit cost and time of communication invariant in terms of distance.”
Why relevant

Explains satellite and cell-phone usage as forms of communication that do not rely on physical transport lines, illustrating the concept of non-wire (wireless) links over distance.

How to extend

A student can use this pattern of non-physical-link communications to test whether LiFi, which communicates via a propagated medium rather than cables, fits the wireless category.

FUNDAMENTALS OF HUMAN GEOGRAPHY, CLASS XII (NCERT 2025 ed.) > Chapter 6: Tertiary and Quaternary Activities > Communication > p. 48
Strength: 4/5
“Communication services involve the transmission of words and messages, facts and ideas. The invention of writing preserved messages and helped to make communication dependent on means of transport. These were actually carried by hand, animals, boat, road, rail and air. That is why all forms of transport are also referred to as lines of communication. Where the transport network is efficient, communications are easily disseminated. Certain developments, such as mobile telephony and satellites, have made communications independent of transport. All forms are not fully disassociated because of the cheapness of the older systems. Thus, very 48 Fundamentals of Human Geography”
Why relevant

Notes that developments like mobile telephony and satellites have made communications independent of transport, implying ‘wireless’ methods remove the need for physical transmission lines.

How to extend

Apply the general rule that technologies removing dependence on physical lines are 'wireless' and check if LiFi similarly avoids physical conductors by using light propagation.

Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 14: Service Sector > Communication Sector > p. 432
Strength: 3/5
“The communication service is defined as the transmission of messages, particularly sending and receiving information. Development of satellite communication and mobile technologies gives prominence to this sector.”
Why relevant

Defines communication broadly as the transmission of messages/information, providing a conceptual framework for categorising different transmission media (wired vs wireless).

How to extend

Using this definition, a student can classify LiFi by identifying its transmission medium (light) and deciding whether that medium constitutes a wireless channel.

Statement 3
Are typical LiFi data transmission speeds several times higher than typical WiFi speeds?
Origin: Weak / unclear Fairness: Borderline / guessy
Indirect textbook clues
Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.2 The Refractive Index > p. 148
Strength: 4/5
“In air, the speed of light is only marginally less, compared to that in vacuum. It reduces considerably in glass or water. The value of the refractive index for a given pair of media depends upon the speed of light in the two media, as given below. Consider a ray of light travelling from medium 1 into medium 2, as shown in Fig.9.11. Let v1 be the speed of light in medium 1 and v2 be the speed of light in medium 2. The refractive index of medium 2 with respect to medium 1 is given by the ratio of the speed of light in medium 1 and the speed of light in medium 2.”
Why relevant

Explains that light travels at (nearly) the maximum possible speed in air/vacuum and slows in denser media, highlighting that light-based systems can use a very fast carrier.

How to extend

A student could combine this with the fact that LiFi uses visible/infrared light as carrier to infer potential for high raw signaling rates relative to radio carriers.

Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 15: Infrastructure > National Optical Fibre Network (NOFN) > p. 463
Strength: 4/5
“• The project envisages an optimal mix of optical fibre, radio and satellite media. ۰• The aim is to establish a highly scalable network infrastructure accessible on non-discriminatory basis, affordable broadband connectivity of 2 Mbps to 20 Mbps for all households. Till August 2019, 1.25 lakh GPs were already connected with high-speed broadband connectivity under BharatNet.”
Why relevant

Gives concrete bandwidth/throughput targets for broadband (2–20 Mbps) over optical/radio/satellite mixes, providing a baseline for typical consumer network speeds.

How to extend

Compare these stated broadband speeds to published peak/typical speeds claimed for LiFi and WiFi to judge whether LiFi could be multiple times faster in practice.

Science-Class VII . NCERT(Revised ed 2025) > Chapter 8: Measurement of Time and Motion > 8.4 Uniform and Non-uniform Linear Motion > p. 117
Strength: 3/5
“That is why we have to use average speeds.”
Why relevant

Notes the use of average speeds when motion (or rates) vary, illustrating a general method for comparing technologies using average/typical values rather than peaks.

How to extend

A student should compare average (not peak) throughput measurements for LiFi and WiFi from real deployments to assess the 'several times' claim.

Science-Class VII . NCERT(Revised ed 2025) > Chapter 8: Measurement of Time and Motion > Table 8.2: Finding the speed of trains > p. 115
Strength: 3/5
“Compare the speeds of the trains. Which is the fastest train? The train which has covered the maximum distance in unit time”
Why relevant

Defines comparing speeds by distance covered in unit time (i.e., a clear comparative rule for rates), a transferable idea for comparing data rates (bits per second).

How to extend

Translate the principle to data: compare bits transmitted per second for LiFi vs WiFi under similar conditions to test the statement.

Science-Class VII . NCERT(Revised ed 2025) > Chapter 8: Measurement of Time and Motion > Let Us Enhance Our Learning > p. 119
Strength: 2/5
“• 8. A car covers 60 km in the fi rst hour, 70 km in the second hour, and 50 km in the third hour. Is the motion uniform? Justify your answer. Find the average speed of the car.• 9. Which type of motion is more common in daily life uniform or non-uniform? Provide three examples from your experience to support your answer.• 10. Data for the motion of an object are given in the following table. State whether the speed of the object is uniform or non-uniform. Find the average speed. • Time (s): Distance (m); 0: 0; 10: 6; 20: 10; 30: 16; 40: 21; 50: 29; 60: 35; 70: 42; 80: 45; 90: 55; 100: 60 11.”
Why relevant

Provides examples and exercises about computing and comparing speeds, reinforcing that meaningful comparison requires consistent metrics and contexts.

How to extend

Use the same approach—pick consistent test conditions (typical devices, distances, interference) and compute average data rates for LiFi and WiFi to evaluate the claim.

Pattern takeaway: UPSC S&T questions follow a 'Definition + Benefit' template. Statement 1 defines the mechanism (Light), and Statement 2 claims the benefit (Faster). For emerging technologies, 'optimistic' statements about speed and efficiency are statistically likely to be correct.
How you should have studied
  1. [THE VERDICT]: Current Affairs Sitter. If you followed the S&T page of The Hindu in 2015-16, this was basic. If you relied only on static physics NCERTs, it was a Bouncer.
  2. [THE CONCEPTUAL TRIGGER]: Evolution of Communication Technology. UPSC consistently compares incumbent tech (WiFi, 4G, CFL) with challengers (LiFi, 5G, LED).
  3. [THE HORIZONTAL EXPANSION]: Map the Wireless Spectrum: NFC (Induction, <4cm), Bluetooth (2.4GHz, ~10m), WiFi (2.4/5GHz, ~50m), LiFi (Visible Light 400-800 THz, Line-of-Sight only). Key differentiator: LiFi cannot penetrate walls; WiFi can.
  4. [THE STRATEGIC METACOGNITION]: When studying new tech, extract three things: 1. The Mechanism (Light vs Radio waves), 2. The Comparative Advantage (100x faster), and 3. The Fatal Flaw (Needs Line of Sight/blocked by walls).
Concept hooks from this question
📌 Adjacent topic to master
S1
👉 Optical media in telecommunications
💡 The insight

Evidence [8] names optical fibre alongside radio and satellite as media used to provide high‑speed broadband, directly linking light‑based channels to data transmission.

High yield for UPSC technical/technology questions: explains how modern networks deliver broadband and why optical solutions are prioritized. Connects to infrastructure, digital connectivity and policy topics (BharatNet/NOFN). Study by mapping media types (optical, radio, satellite), their roles, and policy initiatives.

📚 Reading List :
  • Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 15: Infrastructure > National Optical Fibre Network (NOFN) > p. 463
🔗 Anchor: "Does LiFi use light (visible light or optical spectrum) as the medium for high-s..."
📌 Adjacent topic to master
S1
👉 Directed light sources (lasers/visible beams)
💡 The insight

References describe laser beams and visible light sources ([9],[4]), highlighting that light can be produced in controlled, directed form suitable for transmission.

Useful for questions on communication technologies (LiFi, free‑space optics) and physics of signal propagation. Helps answer why light can carry information and where line‑of‑sight or beam control matters. Prepare by linking physical properties of lasers/LEDs to communication use‑cases.

📚 Reading List :
  • Science-Class VII . NCERT(Revised ed 2025) > Chapter 11: Light: Shadows and Reflections > Activity 11.1: Let us investigate > p. 156
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > 5.8.r. Causes > p. 81
🔗 Anchor: "Does LiFi use light (visible light or optical spectrum) as the medium for high-s..."
📌 Adjacent topic to master
S1
👉 Speed of light & optical properties of media (refractive index)
💡 The insight

References on refractive index and speed of light in media ([2],[3],[6]) explain how light behaves in different media, relevant to optical transmission (e.g., fibres) and signal design.

Covers core physics underlying optical communications and fibre design—frequently useful in interdisciplinary UPSC questions integrating science and technology. Master by understanding refractive index, speed variations, and how they affect propagation and coupling of light.

📚 Reading List :
  • Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > Activity 9.10 > p. 149
  • Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.2 The Refractive Index > p. 148
  • Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > What you have learnt > p. 159
🔗 Anchor: "Does LiFi use light (visible light or optical spectrum) as the medium for high-s..."
📌 Adjacent topic to master
S2
👉 Wireless communication: definition & examples
💡 The insight

References describe radio, mobile phones and satellites as forms of wireless communication — core idea needed to judge whether a technology like LiFi would be classed as ‘wireless’.

High-yield for UPSC because questions often ask about types/modes of communication and their societal impact. Connects to telecom infrastructure, digital access and media topics. Prepare by memorising definitions, listing major wireless media (radio, mobile, satellite) and contrasting wired vs wireless.

📚 Reading List :
  • Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 12: Transport, Communications and Trade > Radio, Television, and Cinema > p. 44
  • FUNDAMENTALS OF HUMAN GEOGRAPHY, CLASS XII (NCERT 2025 ed.) > Chapter 6: Tertiary and Quaternary Activities > Telecommunications > p. 49
  • Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 15: Infrastructure > TELECOM SECTOR > p. 462
🔗 Anchor: "Is LiFi a wireless communication technology?"
📌 Adjacent topic to master
S2
👉 Satellite communication: role and features
💡 The insight

References highlight satellites enabling long-distance/mobile/internet communication and connecting remote areas — illustrates one major non-wired medium.

Frequently tested in geography/infrastructure and technology policy contexts (connectivity, rural access). Helps answer questions about network reach, cost/time invariance with distance, and policy interventions. Study operational roles, advantages/limitations and their policy implications.

📚 Reading List :
  • FUNDAMENTALS OF HUMAN GEOGRAPHY, CLASS XII (NCERT 2025 ed.) > Chapter 7: Transport and Communication > Satellite Communication > p. 68
  • Understanding Economic Development. Class X . NCERT(Revised ed 2025) > Chapter 4: GLOBALISATION AND THE INDIAN ECONOMY > Containers for transport of goods > p. 62
🔗 Anchor: "Is LiFi a wireless communication technology?"
📌 Adjacent topic to master
S2
👉 Mobile telephony & wireless penetration in India
💡 The insight

References provide data and commentary on wireless telephone connections and the mobile industry’s contribution — concrete evidence of wireless uptake and policy relevance.

Useful for economy and infrastructure questions (telecom policy, digital services, GDP linkage). Learn key statistics, growth drivers, and implications for services and regulation to answer value-added or data-based questions in the exam.

📚 Reading List :
  • Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 15: Infrastructure > TELECOM SECTOR > p. 462
  • FUNDAMENTALS OF HUMAN GEOGRAPHY, CLASS XII (NCERT 2025 ed.) > Chapter 6: Tertiary and Quaternary Activities > Telecommunications > p. 49
🔗 Anchor: "Is LiFi a wireless communication technology?"
📌 Adjacent topic to master
S3
👉 Refractive index & speed of light in media
💡 The insight

LiFi uses light for data transmission; reference [4] explains that light speed changes in different media via refractive index, which is relevant to how optical signals propagate.

Understanding refractive index and light speed is high-yield for linking basic optics to optical communication technologies (e.g., LiFi, fiber). It helps reason about signal propagation, attenuation and medium-dependent limits without needing device-specific specs. Master via NCERT optics chapters and applied examples.

📚 Reading List :
  • Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.2 The Refractive Index > p. 148
🔗 Anchor: "Are typical LiFi data transmission speeds several times higher than typical WiFi..."
🌑 The Hidden Trap

The 'Next Logical Question' focuses on limitations. Since LiFi uses visible light, it cannot pass through opaque objects (walls). This makes it more secure (hack-proof from outside) but less convenient than WiFi. Also, look out for 'Free Space Optical Communication' (FSOC) which uses lasers for long-distance links.

⚡ Elimination Cheat Code

Use the 'Etymology + Optimism' Hack. 'LiFi' literally stands for Light Fidelity—validating Statement 1 immediately. For Statement 2, apply the 'Tech Upgrade Rule': New technologies make news *because* they are faster or better. If LiFi were slower than WiFi, it wouldn't be a prelims topic. Therefore, 'several times faster' is intuitively true.

🔗 Mains Connection

Link to GS-3 Infrastructure & Security: LiFi solves the 'Spectrum Crunch' crisis (Radio Frequency spectrum is congested/expensive; Visible Light spectrum is vast/unlicensed). It also enhances Cyber Security in sensitive zones (nuclear plants, defense HQs) because signals don't leak through walls.

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