Defence GK Questions 2026

The first two members of the family, Sri Gupta and Ghatotkacha, used only the modest title Maharaja, which historians read as a sign that they were subordinate rulers.

Gupta gold coins were called dinaras, a name borrowed from the Roman denarius that had already reached India through trade and through Kushana coinage.

Gupta imperial rule is conventionally dated from about 320 CE, the epoch of the Gupta era that begins with the accession of Chandragupta I, and it faded out by about 550 CE after the Huna invasions.

The continental shelf is the gently sloping submerged edge of a continent, usually taken down to about two hundred metres.

Its southern end holds the Challenger Deep, the deepest surveyed point on earth at roughly eleven kilometres below sea level, deep enough to swallow Mount Everest with water to spare.

Sodium chloride makes up most of it, with magnesium, calcium and potassium salts making up the rest. Salinity varies with evaporation, rainfall, river inflow and the melting or freezing of ice, so the figure is an average rather than a fixed value.

The warm Gulf Stream moving north-east meets the cold Labrador current coming south past Newfoundland. Nutrients carried by the cold water mix with the warmer surface layer, plankton multiplies, and huge shoals of cod once gathered there.

It flows northward along the western coast of southern Africa, carrying cool water from the Southern Ocean towards the equator, and the upwelling along it makes the Namibian coast a rich fishing zone while helping to keep the Namib desert dry.

The bay narrows and shallows inland, so the incoming tidal wave is funnelled into a smaller and smaller cross-section and its height is greatly magnified, giving the greatest difference between high and low water anywhere on earth.

Spring tides occur at new moon and at full moon, when the sun, the earth and the moon lie in a straight line, a position called syzygy.

Textbooks describing the distribution of water on earth give about 97.2 per cent as ocean water, roughly 2 per cent locked in ice caps and glaciers, and well under 1 per cent as groundwater, lakes, rivers, soil moisture and water vapour together.

The Ring of Fire is a horseshoe-shaped belt running around the rim of the Pacific Ocean, from the Andes up the west coast of the Americas, across the Aleutians and down through Japan, the Philippines and Indonesia to New Zealand.

El Nino, Spanish for the child, is the warm surface water that appears off the coast of Peru and Ecuador around Christmas in some years, replacing the normally cold Peru or Humboldt current.

It is a warm current of the Indian Ocean that flows southward along the eastern coast of southern Africa, carrying tropical water towards the Cape before most of it turns back into the Indian Ocean.

The sensation of a sound persists in the human brain for roughly one tenth of a second, so a reflected sound must arrive at least that much after the original to be heard as a separate echo.

SONAR stands for Sound Navigation and Ranging. A transmitter on the ship sends short ultrasonic pulses into the water, the pulses are reflected from the sea bed, a submarine, an iceberg or a shoal of fish, and a detector records the returning echo.

Sound travels fastest in solids because their particles are packed closely and are strongly bound, so a disturbance is passed on to the next particle almost at once.

This is the band of frequencies to which a healthy human ear responds, and the upper limit falls with age.

A vacuum contains no particles, and a mechanical wave such as sound can travel only by making particles vibrate and hand the disturbance on to their neighbours.

In a sound wave the particles of the medium vibrate back and forth along the same line in which the wave is travelling, producing regions where they crowd together, called compressions, and regions where they spread apart, called rarefactions.