Science & Technology — PPSC previous year questions

Oilzapper is a bioremediation product developed by TERI. It is a set of hydrocarbon-degrading bacteria fixed on a carrier material. It is sprayed on oily sludge and oil spills, and it breaks the hydrocarbons down into carbon dioxide and water. Refineries and ONGC use it to clean up crude-oil contamination. So it is a clean-up technology. It is not an exploration technique, a crop variety or a fire-control device.

Maglev (magnetic levitation) trains use strong electromagnets. These lift the train above the guideway and drive it without wheel-rail friction. This allows very high speeds, as on the Shanghai Maglev. The other pairs are wrong. Aspartame is an artificial sweetener, not a salt. Graphene is a one-atom-thick allotrope of carbon, not fluorine. Quantum dots are nanometre-sized semiconductor crystals used in displays and imaging, not spots on the Sun or Jupiter.

The UV lamp in a water purifier is germicidal: light of about 254 nm damages the DNA of bacteria, viruses and protozoa so they cannot multiply. UV adds nothing to the water and removes nothing from it, so it cannot take out odours, settle suspended solids or change the taste; those jobs need coagulation and sedimentation, sediment or activated-carbon filters, or an RO membrane. Only statement (i) is correct.

Starlink is the low-Earth-orbit satellite internet constellation built and operated by SpaceX, Elon Musk's company, with launches beginning in 2019 and thousands of satellites in orbit. Amazon's rival project is Kuiper, and Blue Origin (Jeff Bezos) is a launch-vehicle company.

Statements I, II and III are the usual reasons given for the Nano Mission. Nano-formulations raise agricultural productivity. Nanofibres and nano-membranes purify water and treat toxic waste. Nanoparticles allow early diagnosis and targeted drug delivery. Statement IV is wrong. The very smallness of nanomaterials is a known health concern. They can cross cell membranes, make free radicals and damage DNA. So there is no 'absolute zero risk'. So I, II and III only.

5G offers far higher data rates and very low latency (about one millisecond), which is what makes real-time telemedicine, remote surgery and interactive digital classrooms practical, so statement 1 is correct. Statement 2 says the opposite of the truth. Analog 'brick phones' belong to 1G of the 1980s, so statement 3 is absurd. LTE is the 4G standard and 5G fully supports VPNs, so statement 4 is also false. Only statement 1 stands.

Ethanol is produced by fermenting sugars or starch, so corn (maize), sugar beet and cassava are all standard feedstocks. India's National Policy on Biofuels (2018, amended 2022) also permits damaged and surplus food grains unfit for human consumption to be used for ethanol.

C.V. Raman explained inelastic scattering of light (the Raman effect), S. Chandrasekhar worked on stellar evolution and white dwarfs (the Chandrasekhar limit), S.N. Bose's statistics underlie the Bose-Einstein condensate, and J.C. Bose invented the crescograph and studied electromagnetic waves. The order is Q, P, R, S.

A gravitational wave is picked up by several detectors a fraction of a second apart. Adding a detector in India, far from the others, helps to pin down where in the sky the wave came from — this is called source localisation. It does not change the frequencies detected or find waves in the cosmic microwave background.

CRISPR-Cas9 is a gene-editing tool. A guide RNA takes the Cas9 enzyme to a chosen DNA sequence. There Cas9 cuts both strands, so the gene can be disabled, corrected or replaced. Jennifer Doudna and Emmanuelle Charpentier got the 2020 Nobel Prize in Chemistry for developing it. Gene identification, protein–protein interaction studies and genome mapping only study genes. They do not edit them.