Which one of the following statements is true for James Webb Space Telescope launched in December 2021?

The correct answer is B, a 50,000-tonne magnetised Iron CALorimeter, known as ICAL and read out by resistive plate chambers. Placed in a cavern under about 1,300 metres of rock at Pottipuram in the Bodi West Hills, it is designed to catch atmospheric neutrinos and measure how they change from one flavour to another, the phenomenon of neutrino oscillation; the magnetic field lets it tell a neutrino from an antineutrino. Option A, a water Cherenkov tank, is the design of Super-Kamiokande in Japan, not of ICAL. Option C, a liquid argon time projection chamber, is the technology of the American DUNE experiment. Option D, a superconducting tokamak, is a fusion machine such as India SST-1 and has nothing to do with neutrinos. The host institute of the observatory is the Tata Institute of Fundamental Research, and India already recorded atmospheric neutrinos in the Kolar Gold Fields mines in 1965.

The correct answer is A, Aundha in the Hingoli district of Maharashtra. The site was chosen for its flat, seismically quiet ground, the Union Cabinet approved the project in principle in 2016 and in full in April 2023, and it is being executed by the Department of Atomic Energy and the Department of Science and Technology with IPR, RRCAT Indore and IUCAA Pune. Option B, Hanle in Ladakh, is an astronomy site: it hosts the Indian Astronomical Observatory and the MACE gamma-ray telescope. Option C, Pottipuram in Theni district, is the planned site of the India-based Neutrino Observatory, a different mega science project. Option D, Khodad near Pune, is where the Giant Metrewave Radio Telescope stands. Keep the pairs apart: gravitational waves at Hingoli, neutrinos at Theni, radio astronomy at Khodad and optical astronomy at Hanle.

The correct answer is B, Albert Einstein. Gravitational waves are ripples in space-time thrown out by violent events such as the merger of two black holes, and they follow from the general theory of relativity that Einstein published in 1915, with the prediction of the waves set out in 1916. LIGO recorded the first direct signal on 14 September 2015 and announced it in February 2016, and the Nobel Prize in Physics of 2017 went to Rainer Weiss, Barry Barish and Kip Thorne. Option A, Isaac Newton, gave the inverse square law of gravitation in which gravity acts instantly and no waves exist. Option C, Niels Bohr, worked on the atom and quantum theory. Option D, Stephen Hawking, is famous for black hole radiation and cosmology, which is why his name tempts candidates, but he was born well after the prediction was made.

The correct answer is C. Fusion is the joining of two light nuclei into a heavier one, with a neutron or other products released and a large amount of energy appearing because the mass of the product is slightly less than the mass of the reactants; in ITER the reaction fuses deuterium and tritium into helium and a neutron. Option A is wrong because a light nucleus struck by thermal neutrons does not usefully break up; slow neutron induced splitting works on heavy fissile nuclei. Option B describes nuclear fission, the splitting of a heavy nucleus such as uranium-235 by thermal neutrons, which is the reverse of fusion. Option D describes spontaneous fission, in which a very heavy nucleus divides by itself without being struck, a form of radioactive decay. Fusion needs enormous temperature and pressure to overcome the electrical repulsion of the two nuclei, which is why a tokamak confines the plasma with magnetic fields.

The correct answer is A, thermal fusion. A hydrogen bomb, also called a thermonuclear bomb, uses a fission explosion only as a trigger; the main energy comes from the fusion of the heavy hydrogen isotopes deuterium and tritium into helium at temperatures of millions of degrees, which is why the process is described as thermonuclear or thermal fusion. The same reaction powers the Sun and is the reaction ITER is built to tame for peaceful energy. Option B, heavy water ability, is not a nuclear process at all; heavy water is a moderator and coolant used in Indian pressurised heavy water reactors. Option C, thermal fission, is the splitting of a heavy nucleus such as uranium-235 by slow neutrons and is the process of an atom bomb and of ordinary nuclear power stations. Option D, a breeder reaction, is fission that produces more fissile material than it consumes, as in a fast breeder reactor.