Day-599 | Daily MCQs | UPSC Prelims | SCIENCE AND TECHNOLOGY

Answer: D
Explanation
What is radiocarbon dating?
Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was developed in the late 1940s at the University of Chicago by Willard Libby.
Concept of radiocarbon dating
It is based on the fact that radiocarbon (14C) is constantly being created in the Earth’s atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting 14C combines with atmospheric oxygen to form radioactive carbon dioxide, which is incorporated into plants by photosynthesis; animals then acquire 14C by eating the plants. When the animal or plant dies, it stops exchanging carbon with its environment, and thereafter the amount of 14C it contains begins to decrease as the 14C undergoes radioactive decay.
Statement 1 is incorrect: This technique is used to determine the age of objects which are generally of archaeological importance and have organic content (or in simpler words objects which once were living, or material made from living things).
Statement 2 is correct: This technique is used for entities which are dead. When an entity dies, it stops exchanging radiocarbon with the environment. Thus, as the fossil ages, the radiocarbon decays in its concentration. This radioactive decay is analysed to identify the relative age of the fossil.

Answer: A
Explanation
Statement 1 is correct: An air conditioner is typically composed of two units: The indoor and outdoor unit. These are usually called ‘split’ air conditioners. Indoor unit have expansion valve and evaporator coils where outdoor have compressor and condenser coils.

Statement 2 is correct and is the explanation of statement 1: Due to very low vaporization temperature of an AC coolant. The liquid coolant absorbs heat from the room and vaporizes into a gas in the evaporator coil. This leads to a cooling effect in the room. The gaseous form of the coolant is brought back to the liquid state in the condenser coil and by the action of compressor which compresses the gas to again liquify it. This is a continuous cycle and hence, an air conditioner works in this way.

Answer: B
Explanation
• In the current universe, nearly 70 per cent constitutes dark energy whereas 25 per cent is dark matter – about both of which there is scanty knowledge, till date.
• Unlike normal matter, dark matter does not interact with electromagnetic force.
• This means it does not absorb, reflect or emit light, making it extremely hard to spot.
• In fact, researchers have been able to infer the existence of dark matter only from the gravitational effect it seems to have on visible matter.

Answer: B
Explanation
A laser is a device that emits a beam of coherent light through an optical amplification process. The letters in the word laser stand for Light Amplification by Stimulated Emission of Radiation. Lasers produce a narrow beam of light in which all of the light waves have very similar wavelengths.
The laser’s light waves travel together with their peaks all lined up, or in phase. This is why laser beams are very narrow, very bright, and can be focused into a very tiny spot.
Lasers have many uses. They are used in precision tools and can cut through diamonds or thick metal. They can also be designed to help in delicate surgeries. Lasers are used for recording and retrieving information. They are used in communications and in carrying TV and internet signals. We also find them in laser printers, bar code scanners, and DVD players. They also help to make parts for computers and other electronics.
Option 1 is incorrect: Laser is not used for radar applications. Radar stands for Radio Detection and Ranging. It uses radio waves (and not laser) to determine the distance, angle, and radial velocity of objects relative to the site.
Option 2 is correct: Laser is used for optical fiber communication in case of beaming of high-speed internet.
Option 3 is correct: Laser is used for precision surgery like lasik eye surgery for correcting vision.

Answer: A
Explanation
Statement 1 is incorrect: UPI Lite requires internet service to process transactions but it does not require PIN for each transaction. It is UPI 123 Pay system which has been designed for feature phone users to use UPI without the need for internet.
UPI Lite
UPI LITE is a new payment solution that leverages the trusted NPCI Common Library (CL) application to process low value transactions that have been set at below ₹ 500. User enters the amount, and the money is sent to the party without the need for PIN.
Statement 2 is correct: UPI is a type of Prepaid Instrument which does not require PIN for transactions. It is a kind of wallet-based payment instrument that enables users to load cash digitally before transacting.
Statement 3 is incorrect: A direct debit mandate given for recurring expenses like bill payment, recharge does not require OTP to be filled for every transaction. A Direct Debit mandate, sometimes called a Direct Debit instruction (DDI), is when a customer authorizes you to collect future payments from their account on a predetermined schedule.