Innovations in Science and Technology for UPSC Exam

Short Wave Transmission

Prasar Bharati has asked All India Radio to come up with a proposal to phase out Short Wave (SW) transmitters.

About SW:

• Shortwave radio is radio transmission using shortwave radio frequencies, the range always includes all of the high frequency band (HF), and generally extends from 3-30 MHz (10 to 100 meters), above the medium frequency band (MF), to the end of the HF band.
• Radio waves in the shortwave band can be reflected or refracted from a layer of electrically charged atoms in the atmosphere called the ionosphere.
• Therefore, short waves directed at an angle into the sky can be reflected back to Earth at great distances, beyond the horizon.
• This is called skywave or “skip” propagation, thus shortwave radio can be used for very long distance communication, in contrast to radio waves of higher frequency which travel in straight lines (line-of-sight propagation) and are limited by the visual horizon, about 64 km (40 miles).
• Shortwave radio is used for broadcasting of voice and music to shortwave listeners over very large areas, sometimes entire continents or beyond.
• It is also used for military over-the-horizon radar, diplomatic communication, and two-way international communication by amateur radio enthusiasts.

Advantages of Using Shortwave

Shortwave radio has a huge range – it can be received thousands of miles from the transmitter, and transmissions can cross oceans and mountain ranges. This makes it ideal for reaching nations without a radio network. SW transmissions are easy to receive, too: even cheap, simple radios are able to pick up a signal.

Other mode of Transmission

• Medium-wave radio is generally used for local broadcasts and is perfect for rural communities. With a medium transmission range, it can reach isolated areas with a strong, reliable signal. Medium-wave transmissions can be broadcast through established radio networks – where these networks exist. 
   
• Frequency Modulation (FM) provides a short-range signal – generally to anywhere within sight of the transmitter, with excellent sound quality. It can typically cover the area of a small city or large town – making it perfect for a radio station focusing on a limited geographical area speaking into local issues. While shortwave and medium-wave stations can be expensive to operate, a license for a community-based FM station is much cheaper.
   
• Internet Radio: The rapid development of web-based technology offers huge opportunities for radio broadcasting. Internet-based stations are quick and easy to set up (sometimes taking as little as a week to get up and running and costs a lot less than regular transmissions. And because the internet has no borders, a web-based radio audience can have global reach.

Data Localization
 

1. It is a concept that the personal data of a country’s residents should be processed and stored in that country.
2. Some directives may restrict flow entirely, while others more leniently allow for conditional data sharing or data mirroring – in which only a copy has to be stored in the country.
3. As of now, much of cross-border data transfer is governed by individual bilateral “mutual legal assistance treaties” (MLATs).

The ‘Data’ under debate
 

• Data is any collection of information that is stored in a way so computers can easily read it.
• These days, most people refer to data to mean information about their messages, social media posts, online transactions, and browser searches.
• Big data refers to the immense amount of data that can now be collected, stored, and analysed to find patterns.

Artificial gravity

• A team from the University of Colorado is working on making a device which could create artificial gravity in space
• Artificial gravity is a force that simulates the effect of gravity in a spaceship.
• It is not caused by the attraction to the Earth but is instead caused by acceleration or centrifugal force.
• Artificial gravity or rotational gravity is thus the appearance of a centrifugal force in a rotating frame of reference.
• The research centrifuge is called as ‘Human Eccentric Rotator Device’ (HERD) and the device is compact enough to fit into a small room.
• A rotating circular space station can create artificial gravity.
• The rate of rotation is necessary to duplicate the Earth’s gravity depends on the radius of the circle.
• Future astronauts heading into an artificial-gravity room to spend time on a small revolving system.
• It is built with the aim of counteracting the negative effects of weightlessness.

Optoelectronics

• Optoelectronics is the study and application of electronic devices and systems that source, detect and control light, usually considered a sub-field of photonics.
• In this context, light often includes invisible forms of radiation such as gamma rays, X-rays, ultraviolet and infrared, in addition to visible light.
• Materials such as tungsten diselenide (WSe2) and molybdenum diselenide are being studied keenly for their opto-electronic properties.
• A key property of these materials is photoluminescence, in which the material absorbs light and re-emits it as a spectrum.
• Photoluminescence properties can be used in various devices such as quantum LEDs which can be used in communication and computation.

Photoluminescence: Photoluminescence is a process in which a molecule absorbs a photon in the visible region, exciting one of its electrons to a higher electronic excited state, and then radiates a photon as the electron returns to a lower energy state.

5G Technology

• Essentially, 5G is a set of technical ground rules.
• They define the workings of a cellular network, including the radio frequencies used and how various components like computer chips and antennas handle radio signals and exchange data.
   

What are the advantages?

• Speed – The speed depends on where one is, and which wireless services is used.
• Qualcomm, the wireless chipmaker, said it had demonstrated peak 5G download speeds of 4.5 gigabits a second.
• However, it predicts initial median speeds of about 1.4 gigabits.
• In other words, it would be roughly 20 times faster than the current 4G experience.
• E.g. downloading a typical movie at the median speeds cited by Qualcomm would take 17 seconds with 5G, compared with 6 minutes for 4G
• The speeds will be particularly noticeable in higher-quality streaming video.
   

Latency – There is another kind of speed, a lag known as latency, that may become even more important with 5G.

• The response is not exactly immediate when issuing a command now on a smartphone, such as starting a web search.
• A lag of 50 to several hundred milliseconds is common, partly because signals often must pass between different carrier switching centers.
• 5G, which uses newer networking technology, was designed to reduce this latency down to a few milliseconds.
   
• Reliability – 5G is also designed to deliver signals more reliably than earlier cellular networks.
• [Networks now frequently drop bits of data that are not essential for tasks like watching movies on a phone.]
• This change could bring many benefits, notably in fields such as virtual reality.
• The highest-quality VR applications now typically require bulky headsets that are connected by wire to nearby personal computers that generate 3-D images.
• With 5G, that would be off-loaded wirelessly to other machines, freeing users to move and making it easier to develop goggles the size of eyeglasses.
• In the related field of augmented reality, a smartphone camera could be pointed at a football game to see both live video on the display and superimposed player statistics or other data.
   
• Besides these, 5G’s impact extends to medicine and other fields that increasingly rely on high-speed connections.
• Officials in the United States and China see 5G networks as a competitive edge.
• The faster networks could help spread the use of artificial intelligence and other cutting-edge technologies too.

 Hyperloop

What is Hyperloop Technology?

• Theoretical concept of hyperloop is mooted by maverick techno-entrepreneur Elon Musk in 2013.
• Hyperloop technology promises to move people and goods through low-pressure tubes far faster than commercial air travel, within earthly confines, of course.
• In hyperloop transportation, custom-designed capsules or pods are expected to zip smoothly through continuous steel tubes which are held at partial vacuum.
• The pod which sandwiches the passenger compartment between an air compressor upfront and a battery compartment in the rear is supported by air caster skis at the bottom.
• The skis float on a thin layer of air provided under high pressure, eliminating rolling resistance and allowing for movement of the pods at high speeds. These capsules are expected to be driverless with estimated speeds of 1,000 km/h.
• Linear induction motors that are placed along the tube control the speed of the pod. Electronically-assisted acceleration and braking determines the speed of the capsule.

Hydrogen-powered vehicles over Electric vehicles

• China, Japan and South Korea have set ambitious targets to put millions of hydrogen-powered vehicles on their roads.
• But, Hydrogen fuel cell vehicles (FCVs) have been upstaged by electric vehicles (EVs).
• It becomes a mainstream option due to the success of Tesla Inc’s luxury cars as well as sales and production quotas set by China.
• Critics argue FCVs may never amount to more than a niche technology.
• But proponents counter hydrogen is the cleanest energy source for autos available and with time, it will gain acceptance.
• China, far and away the world’s biggest auto market is aiming for more than 1 million FCVs in service by 2030.
• Japan, a market of more than 5 million vehicles annually, wants to have 800,000 FCVs sold by that time.
• Resource-poor Japan sees hydrogen as a way to greater energy security.
• Driving ranges and refuelling times for FCVs are comparable to gasoline cars, whereas EVs require hours to recharge and provide only a few hundred kilometres of range.
• In general, hydrogen is seen as the more efficient choice for heavier vehicles that drive longer distances.
• However, lack of refuelling stations which are costly to build, is usually cited as the biggest obstacle to widespread adoption of FCVs.
• Consumer worries about the risk of explosions are also a big hurdle.
• Residents in Japan and South Korea have protested against the construction of hydrogen stations.
• This year, a hydrogen tank explosion in South Korea killed 2 people, followed by a blast at a Norway hydrogen station.
• Heavy subsidies are needed to bring prices down to levels of gasoline-powered cars.
• Automakers contend that once sales volumes increase, economies of scale will make subsidies unnecessary.

Indigenous Fuel Cell System

On the occasion of the Council of Scientific and Industrial Research (CSIR) Foundation Day, the President of India recently introduced India’s first indigenously developed high-temperature based Fuel Cell System.

• It is developed under the Public-Private Partnership (PPP) model by the Council of Scientific and Industrial Research (CSIR) in partnership with Indian industries.
• It is built under India’s flagship programme named ‘New Millennium Indian Technology Leadership Initiative (NMITLI)’.

Specifications

• The developed fuel cells are based on High-Temperature Proton Exchange Membrane (HTPEM) technology.
• It is a 5.0 kW fuel cell system that generates power in a green manner.
• It takes methanol or bio-methane as the input and produces heat and water as its bi-products, which can be further used.
• This helps to attain an efficiency that is greater than 70%, which is difficult to achieve by other energy sources.

High-Temperature Proton Exchange Membrane (HTPEM) Technology

• High-Temperature Proton-Exchange-Membrane (HTPEM) is the core of the fuel cells that run above 150 °C. It works on two modes of operation with respect to the source of fuel.
• One mode is based on the conversion of natural gas into Hydrogen by means of steam reforming. This mode is used to fulfill stationary power demands.
• Steam reforming or steam methane reforming is a chemical synthesis process for producing syngas (hydrogen and carbon monoxide) from hydrocarbons such as natural gas.
• The second mode is based on the operation of Hydrogen with Oxygen obtained by the process of electrolysis. This is generally used in the space-related applications.
• Electrolysis is a chemical decomposition process in which an electric current is passed through a liquid or a solution containing ions.

Applications

• This fuel system is most suitable to fulfil distributed stationary power applications demands like in small offices, commercial units, data centres, etc. where highly reliable power is essential with simultaneous requirement for air-conditioning.
• This system will meet the requirement of efficient, clean and reliable backup power generators that are demanded by telecom towers, remote locations, and strategic applications.
• The Fuel Cells fit well in India’s mission of replacing Diesel based Generating (DG) sets with the green and alternate fuels.
• This development is therefore expected to reduce India’s dependence on crude oil.

Dark Fibre

Three major telecom service providers, Reliance Jio Infocomm, Bharti Airtel and Vodafone Idea, have approached the state-run Bharat Broadband Network Limited (BBNL) to use its dark fibre. It will help the telecom service providers to cut down on their capital expenditure.

• The unused infrastructure of BBNL will be used to expand the presence in rural India and offer 4G as well as other long-term evolution (LTE) mobile telephony services.

Dark fibre

• It is an unused optical fibre that has been laid but is not currently being used in fibre-optic communications. Since fibre-optic cable transmits information in the form of light pulses, a “dark” cable refers to one through which light pulses are not being transmitted.
• Companies lay extra optical fibres in order to avoid cost repetition when more bandwidth is needed.
• It is also known as unlit fibre.

Bharat Broadband Network Limited

• It is a Special Purpose Vehicle set up by the Government of India under the Companies Act, 1956 with an authorized capital of ₹1000 crore.
• It comes under the Ministry of Communications and Information Technology.
• In 2011, it was mandated to create the National Optical Fiber Network (NOFN) in India which was later renamed as the BharatNet project in 2015.

Elastocaloric Effect
 

When rubbers bands are twisted and untwisted, it produces a cooling effect. This is called the “elastocaloric” effect, and it has been suggested that it can be used in a very relevant context today.

How will it work in a fridge?

• Researchers have found that the elastocaloric effect, if harnessed, may be able to do away with the need of fluid refrigerants used in fridges and air-conditioners. These fluids are susceptible to leakages, and can contribute to global warming. 
• In the elastocaloric effect, the transfer of heat works much the same way as when fluid refrigerants are compressed and expanded. When a rubber band is stretched, it absorbs heat from its environment, and when it is released, it gradually cools down.
• In order to figure out how the twisting mechanism might be able to enable a fridge, the researchers compared the cooling power of rubber fibres, nylon and polyethylene fishing lines and nickel-titanium wires. They observed high cooling from twist changes in twisted, coiled and supercoiled fibres.
• They reported that the level of efficiency of the heat exchange in rubber bands “is comparable to that of standard refrigerants and twice as high as stretching the same materials without twisting”.
• The findings may lead to the development of greener, higher-efficiency and low-cost cooling technology.

TechSagar

1. It is a platform to discover India’s technological capability through a portal.
2. It is a consolidated and comprehensive repository of India’s cyber tech capabilities which provides actionable insights about capabilities of the Indian Industry, academia and research across 25 technology areas like internet of things (IoT), Artificial Intelligence (AI), Machine Learning (ML), blockchain, cloud & virtualisation, robotics & automation, ar/vr, wireless & networking, and more.
3. The portal will list business and research entities from the IT industry, startups, academia, and individual researchers.

Significance:

• The repository will facilitate new opportunities for businesses and academia to collaborate, connect and innovate in future.
• TechSagar will allow targeted search, granular navigation and drill down methods using more than 3000 niche capabilities. As of now, the repository features 4000+ entities from industry, academia and research including large enterprises and start-ups providing a country level view of India’s cyber competencies.

TYRE PYROLYSIS

About:

• What is it? Tyre pyrolysis refers to a technique of breaking down used tyres in the absence of oxygen. Shredded tyres, at temperatures between 250º C and 500º C, produce liquid oil and gases.
• NGT Ruling (2014): The National Green Tribunal in 2014 prohibited used tyres from being burnt in the open or being used as fuel in brick kilns, because of the toxic emissions. Subsequently, the board issued a set of guidelines, in which pyrolysis was recommended as an acceptable mode.
• Health risks: While this is considered a safer technique than burning tyres, pyrolysis leaves fine carbon matter, pyro-gas and oil as residue and the inadequate management of these by-products poses health risks. 

Biorock or mineral accretion technology

What is Biorock?

It is the name given to the substance formed by electro accumulation of minerals dissolved in seawater on steel structures that are lowered onto the sea bed and are connected to a power source, in this case solar panels that float on the surface.

How they are formed?

1. The technology works by passing a small amount of electrical current through electrodes in the water.
2. When a positively charged anode and negatively charged cathode are placed on the sea floor, with an electric current flowing between them, calcium ions combine with carbonate ions and adhere to the structure (cathode).
3. This results in calcium carbonate formation. Coral larvae adhere to the CaCO3 and grow quickly.
4. Fragments of broken corals are tied to the biorock structure, where they are able to grow at least four to six times faster than their actual growth as they need not spend their energy in building their own calcium carbonate skeletons.

Lithium-Sulfur Battery

• Researchers who have developed this new Li-S battery claim it has an “ultra-high capacity” and has better performance and less environmental impact.
• This means that they may be able to outperform the Li-ion batteries by more than four times.
• With Li-ion batteries, some disadvantages include their susceptibility to overheating and their being prone to damage at high voltages.
• Such batteries also start losing their capacity over time — for instance, a laptop battery in use for a few years does not function as well as a new one.

Construction
 

While the materials used in the Li-S batteries are not different from those in Li-ion batteries, the researchers have reconfigured the design of the sulfur cathodes (a type of electrical conductor through which electrons move) to accommodate higher stress without a drop in overall capacity.

Advantages of the Li-S batteries

• Li-S batteries are generally considered to be the successors of the Lithium-ion (Li-ion) batteries because of their lower cost of production, energy efficiency and improved safety.
• Their cost of production is lower because sulfur is abundantly available.
• Even so, there have been some difficulties when it comes to commercialising these batteries, mainly due to their short life cycle and poor instantaneous power capabilities.

Why is this development important?

• As the market share of electric vehicles (EV) is increasing and people are becoming more aware and conscious of global warming and climate change.
• There is a need for development in terms of the kind of batteries used in these vehicles.
• The growth of the EV market is linked to the development of batteries that are cost-effective, more efficient and leave a smaller environmental burden.
• Today, most EV use Li-ion batteries, but are slowly reaching their theoretical limits of being able to provide roughly up to 300-watt hour per kilogram of energy.
• Thus arises the need for batteries that can store more energy to run these cars, and Li-S batteries are considered to be a good alternative.

Lithium-ion batteries

Nobel Prize in chemistry 2019 awarded for work on lithium-ion batteries

About

• The first rechargeable battery came about in 1859. These were made from lead-acid, and are still used to start gasoline- and diesel-powered vehicles today.
• Stanley Whittingham discovered an extremely energy-rich material, which he used to create an innovative cathode in a lithium battery. This battery was made from titanium disulphide.
• The battery’s anode was partially made from metallic lithium, which has a strong drive to release electrons. It resulted in a battery that had great potential, just over two volts.
• The big advantage of this technology was that lithium-ion stored about 10 times as much energy as lead-acid or 5 times as much as nickel-cadmium
• Lithium-ion batteries were also extremely lightweight and required little maintenance.
• Lithium ion batteries using cobalt oxide can boost the lithium battery’s potential to four volts.

Benefits and uses:

• The advantage of lithium-ion batteries is that they are not based upon chemical reactions that break down the electrodes, but upon lithium ions flowing back and forth between the anode and cathode.
• They are lightweight, rechargeable, powerful batteries, now used in everything from mobile phones to laptops and long-range electric vehicles.
• Battery technology helps replace carbon-emitting sources because it allows power companies to store excess solar and wind power when the sun does not shine nor the wind blow, making possible a fossil fuel-free society and combating the effects of climate change.
• They are also capable of being miniaturized and used in devices like implanted pacemakers.
• They can be scaled up to power a car or a home.

Mechanics of Lithium ion battery:

• Lithium-ion batteries are powered by flows of lithium ions crossing from one material to another.
• When the battery is in use, positively-charged lithium ions pass from an anode to a cathode, releasing a stream of electrons along the way that form an electric current.
• When the battery is being recharged, lithium ions flow in the opposite direction, resetting the battery to do it all over again.

Issues and concerns:

• The demand for lithium is spiking and will continue to increase as more battery-powered cars and storage units hit the market.
• Lithium mining requires millions of gallons of water and in places like Tibet and dry regions of South America, selling water became a dirty business.
• Poorly run mines can also contaminate local water supplies.
• Cobalt is also in short supply, and mining of that metal in places like the Congo Basin is driving environmental destruction, child labour, and pollution.
• More than half of lithium is gathered using brine extraction from deep inside the earth, and the rest is still mined traditionally from rock.
• Both methods have caused environmental damage to areas around lithium processing operations.
• And as the demand for lithium increases, companies may resort to using energy-intensive heating to speed up brine evaporation.
• Once lithium-ion batteries are used up in electronics, they are often disposed of improperly by consumers. Only a small percentage is collected and recycled. Most end up in landfills.
• Recycling the batteries and removing these increasingly precious metals is also costly and sometimes dangerous.
• There are a limited number of times that a lithium-ion battery can be replenished before it deteriorates and can no longer hold a charge.
• In addition, a faultily designed lithium-ion battery can turn into a miniature bomb.
• Technologists often point to lithium-ion as an innovation roadblock: there’s not much that engineers can do beyond making the batteries bigger and implementing software algorithms to make hardware more power efficient.

Quantum supremacy

It is a term proposed in 2012 by John Preskill, professor of theoretical physics at the California Institute of Technology.

It describes the point where quantum computers can do things that classical computers cannot.

In Google’s case, researchers at the University of California, Santa Barbara have claimed to have developed a processor that took 200 seconds to do a calculation that would have taken a classical computer 10,000 years.

What are qubits?

A qubit is the physical carrier of quantum information and can take values of zero, one, or both at once.

Classical computes encode information in bits whereas quantum computers use qubits.

Each qubit can represent both a 1 and a 0 at the same time.

Using qubit, Quantum Computers can hold more information than classical computers and solve problems faster and more efficiently.

In designing a standard computer, engineers spend a lot of time trying to make sure the status of each bit is independent from that of all the other bits.

But in a quantum computer, each qubit influences the other qubits around it, working together to arrive at a solution.

Superposition and entanglement are what give quantum computers the ability to process so much more information so much faster.

Difference between a standard computer and a quantum computer:

• A classical computer performs calculations using bits that is 0 representing off and 1 representing on.
• It uses transistors to process information in the form of sequences of zeros and ones called computer binary language. More transistors more processing ability.
• A quantum computer uses the laws of quantum mechanics.
• Just like a classical computer that uses zeros and ones. These states can be achieved in particles due to their internal angular momentum called spin.
• The two states 0 and 1 can be represented in the spin of the particle.
• For example: clockwise spin represents 1 and counter clockwise represents 0. The advantage of using a quantum computer is that the particle can be in multiple states simultaneously. This phenomenon is called
• Due to this phenomenon a quantum computer can achieve both 0 and 1 states at the same time. Thus, in a classical computer information is expressed through single number either 0 or 1.
• A quantum computer uses quits which is described as a 0 and 1 at the same time giving us more processing power.
• For Instance: In a 2 bit classic computer to analyse 00 01 10 11 , it has to grow through each step to get to a result . In a 2-qubit quantum computer can analyse all the possibilities at the same time. Hence reducing time.

Belle – II

• It is an experiment carried out by The High Energy Accelerator Research Organisation, Japan to study violations of the standard model and dark matter.
• It has a highly sensitive particle detector which has better sensitivity, higher than its predecessor, Belle.
• Complementary to the direct search experiments being carried out at the Large Hadron Collider in CERN, Belle-II will indirectly probe new physics using intense electron-positron beams and a sensitive detector.
•  The experiment has a significant Indian participation. The particle detector at the heart of Belle –II has been built by Indian Scientists from Tata Institute of Fundamental Research
• Recently, the experiment has been rolled out. It has a grand collaboration of 700 Scientist from 23 countries.

National Supercomputing Mission

• The National Supercomputing Mission was announced in 2015, with an aim to connect national academic and R&D institutions with a grid of more than 70 high-performance computing facilities at an estimated cost of ₹4,500 crores over the period of seven years.
• It supports the government’s vision of ‘Digital India’ and ‘Make in India’ initiatives.
• The mission is being implemented by the Department of Science and Technology (Ministry of Science and Technology) and Ministry of Electronics and Information Technology (MeitY), through the Centre for Development of Advanced Computing (C-DAC), Pune and Indian Institute of Science (IISc), Bengaluru.
• It is also an effort to improve the number of supercomputers owned by India.
• These supercomputers will also be networked on the National Supercomputing grid over the National Knowledge Network (NKN). The NKN connects academic institutions and R&D labs over a high-speed network.
• Under NSM, the long-term plan is to build a strong base of 20,000 skilled persons over the next five years who will be equipped to handle the complexities of supercomputers.

Progress of NSM:

• NSM’s first supercomputer named Param Shivay has been installed in IIT-BHU, Varanasi, in 2019. It has 837 TeraFlop High-Performance Computing (HPC) capacity.
• The second supercomputer with a capacity of 1.66 PetaFlop has been installed at IIT-Kharagpur.
• The third system, Param Brahma, has been installed at IISER-Pune, which has a capacity of 797 TeraFlop.

Background:

• Teraflops: It is a unit of computing speed equal to one million million (10^12) floating-point operations per second (FLOPS).
• Petaflops: It is a unit of computing speed equal to one thousand million million (10^15) floating-point operations per second (FLOPS).

4D Printing

• Scientists have successfully developed the world’s first 4D printing for ceramics.
• It can be used to create complex, shape-changing objects.
• 4D printing is conventional 3D printing combined with the additional element of time as the 4th dimension.
• The 4D printed objects can re-shape or self-assemble themselves over time with external stimuli, such as mechanical force, temperature, or a magnetic field.
• The existing 3D-printed ceramic productions are usually difficult to deform and hinder the production of ceramics with complex shapes.
• A novel ceramic ink was developed to stretch the ceramic products beyond its initial length and allow complex shapes with heat treatment.

LiFi

• Light-fidelity (LiFi) is a technology used for free-space communication using visible and near-visible light.
• It is similar to Wireless Fidelity (WiFi), a technology for wireless local area network communication using microwaves.
• Microwaves can pass through walls while transmitting signals whereas visible and near-visible light cannot pass through walls.
• Thus it makes LiFi signal network more secure.
• Scientists have recently added a new layer of security to LiFi.
• Light bounces off from walls and falls on the receiver.
• So wall boundaries can be used effectively for reflecting signals so that communication is maintained even without line-of-sight communication between the signal source and receiver.
• Receiving detectors can receive both direct and reflected signals.
• Walls painted with fluorescent and phosphorescent paints absorb and then emit light with marginal loss.
• The paints continue to emit light even several hours after the original source of light has been switched off.
• This makes the communication signal more effective and secure.

Basic Difference between LiFi and WiFi:

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