UPSC GK Questions 2026

It lies in a rift valley in southern Siberia, reaches a depth of about 1,642 metres and holds more fresh water by volume than any other lake, roughly a fifth of the unfrozen surface fresh water of the earth.

A light year is the distance that light travels in vacuum in one year at about 3 into 10 to the power 8 metres per second, which works out to roughly 9.46 into 10 to the power 12 kilometres; astronomers use it because distances between stars are awkward to write…

Visible light runs from about 400 nanometres at the violet end to about 700 nanometres at the red end, so violet has the shortest wavelength, the highest frequency and the greatest energy of the seven colours remembered as VIBGYOR.

Maxwell showed that this speed is fixed by the electric permittivity and magnetic permeability of free space, and its agreement with the measured speed of light was the proof that light is an electromagnetic wave; every band of the spectrum shares the same value in vacuum.

Ozone in the stratosphere absorbs most of the harmful shorter ultraviolet, and that is why the thinning of the layer by chlorofluorocarbons raises the risk of skin cancer, cataract and damage to crops; the small part of ultraviolet that does reach the surface makes vitamin D in human skin.

A remote control carries a small light emitting diode that sends coded pulses of near infrared, which a sensor in the set decodes; the radiation is invisible, harmless at that power and does not pass through walls, so remotes in neighbouring rooms do not interfere.

In 1800 he passed sunlight through a prism and moved a thermometer across the coloured band; the reading went on rising past the red end, which showed the presence of an invisible heating radiation now called infrared.

In 1895 he noticed that a screen coated with a fluorescent salt glowed when a discharge tube was working nearby even though the tube was covered, and he called the unknown radiation X-rays; he received the first Nobel Prize in Physics in 1901 for the discovery.

The spectrum in order of rising wavelength runs gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves and radio waves, and the option follows that sequence with the visible and microwave bands left out.

They have the shortest wavelength of the spectrum and therefore the highest frequency and energy, and being uncharged and very energetic they pass through several centimetres of lead, which is why thick shielding is needed in radiotherapy rooms.

Their wavelength runs from about a tenth of a metre up to many kilometres, which makes them the longest and therefore the lowest in frequency and energy of the whole spectrum; they are used in broadcasting, mobile telephony and radio astronomy.

In an electromagnetic wave the electric field, the magnetic field and the direction of propagation are mutually perpendicular, and because the wave is made of fields and not of vibrating particles it needs no medium, which is how sunlight crosses empty space while sound cannot.

In 1887 he used a spark gap oscillator to generate waves and a loop with a gap to detect them, and he measured their wavelength and showed that they behaved like light in reflection and refraction, which confirmed the theory.

Tides are the regular rise and fall of sea level caused mainly by the gravitational pull of the Moon, and to a lesser extent the Sun, on the Earth.

The Precambrian covers all of Earth's history from its formation about 4.6 billion years ago to the start of the Cambrian about 541 million years ago.

The Caspian has no natural outlet to any ocean, so it is a landlocked water body, in fact the largest inland body of water on Earth.

Parallels shrink as they move towards the poles, so the 0° parallel, the Equator, is the longest of all. Parallels of latitude are circles drawn parallel to the Equator.

Weather maps and reports in India give atmospheric pressure in millibars, the same value as hectopascals. Air pressure is the weight of the air column pressing on a unit area.

The Harmattan blows over West Africa towards the Gulf of Guinea, far from the Mediterranean. The Harmattan is a dry, dusty north-easterly trade wind that blows from the Sahara across West Africa between November and March.

Bronze is an alloy of copper and tin, usually about 88 parts copper to 12 parts tin. Adding tin makes copper harder, stronger and easier to cast, and bronze also resists corrosion well.