NDA GK Questions 2026

A valley glacier reaching the coast scoops its floor below present sea level; when the ice melts and the sea rises, water floods the trough and leaves a long, narrow, steep-sided inlet with great depth.

The term comes from the Kras or Karst plateau of the Dinaric region, which lies largely in present-day Slovenia and extends into the neighbouring coastal belt.

A moraine is the ridge of unsorted rock debris that a glacier carries and dumps; it is named by position as lateral, medial, ground or terminal moraine, and the terminal moraine marks the farthest point the ice reached.

Loess is a depositional landform of wind: very fine silt lifted from desert and glacial margins is carried far away and settles as a yellow, porous, loosely packed sheet.

In its middle and lower course a river swings from side to side, eroding the outer bank of each bend and depositing on the inner bank.

Rainwater charged with carbon dioxide becomes a weak carbonic acid, seeps along joints in limestone and dissolves calcium carbonate by carbonation.

Exfoliation is caused by repeated heating and cooling of the outer layer of a rock and by the release of pressure when overlying material is removed; the surface expands and contracts more than the interior and splits away as curved sheets.

Water erosion passes through stages, and the soil lost grows at every stage. Splash erosion, numbered II, is the first and mildest: raindrops strike bare soil and knock single particles a few centimetres away.

Overgrazing strips the protective cover of grass, loosens the surface with hooves and leaves bare soil exposed to rain and wind, so it is one of the leading causes of soil erosion in dry India, never a remedy.

Bad lands are stretches of land cut into a close network of deep gullies and sharp ridges, so dissected that cultivation becomes impossible, and they are produced when running water removes the topsoil through sheet wash that concentrates first into rills and then into gullies.

Bose designed the crescograph to magnify the growth of a plant many thousand times and record it on a smoked glass plate, which allowed him to show that plants respond to light, heat, touch and other stimuli in ways that resemble responses in animals.

A seismograph holds a heavy mass that tends to stay still while the ground and the frame of the instrument move during a tremor; the relative motion is magnified and traced as a seismogram, from which the arrival times of the primary, secondary and surface waves are read.

In 1895, while working with a discharge tube, Roentgen found an unknown radiation that passed through cardboard and flesh but was stopped by bone and metal, and made a screen coated with a fluorescent salt glow.

In 1928 Fleming noticed that a mould of the genus Penicillium which had contaminated a culture plate in his London laboratory had killed the staphylococcus bacteria around it, and he named the active substance penicillin.

A fathometer, also called an echo sounder, sends a pulse of sound from the hull of a ship to the sea floor and times the returning echo; since the speed of sound in sea water is known, the time gives the depth.

A lactometer is a floating instrument that measures the relative density of milk. Pure milk has a density slightly greater than that of water, so adding water lowers the reading and the float sinks deeper, which is how dilution is detected.

A barometer measures the pressure of the atmosphere, and the mercury barometer invented by Evangelista Torricelli in 1643 does so by balancing the weight of the air against a column of mercury about 76 centimetres high at sea level.

Elektron is the Greek name for amber, the fossilised tree resin which the ancient Greeks found would attract straw, feathers and bits of dust after being rubbed with fur.

Working independently in the 1830s, Michael Faraday in England and Joseph Henry in the United States showed that a changing magnetic flux through a circuit sets up an electromotive force in it, and that the effect depends on the rate of change of flux rather than on the flux itself.

In 1932 Chadwick bombarded beryllium with alpha particles and showed that the highly penetrating radiation given off consisted of neutral particles with almost the same mass as a proton.