NDA GK Questions 2026

The Zollverein was formed in 1834 under Prussian leadership. It removed the internal customs duties that had made trade between the German states slow and costly and reduced the number of currencies in circulation, so a single economic space existed long before a single political one.

As the Franco-Prussian War ended, the German princes assembled in the Hall of Mirrors of the French royal palace at Versailles and proclaimed Wilhelm I of Prussia as German Emperor on 18 January 1871.

Mazzini, a member of the Carbonari who had been sent into exile, founded Young Italy at Marseilles in 1831 and a wider society, Young Europe, at Berne in 1834.

Thomas Young passed light from one source through two narrow slits placed close together and obtained alternate bright and dark bands on a screen.

Polarisation means restricting the vibrations of a wave to one plane, which is only possible if the vibrations are perpendicular to the direction of travel.

The smallest angular separation a telescope can resolve is 1.22 times the wavelength divided by the diameter of the objective, so a larger aperture means a smaller limit of resolution and a greater resolving power.

Diffraction, the bending of a wave round an edge, is appreciable only when the obstacle or opening is of the same order of size as the wavelength.

By Malus's law the intensity transmitted by the second Polaroid is the intensity falling on it multiplied by the square of the cosine of the angle between the two transmission planes.

The fringe width equals the wavelength multiplied by the distance of the screen and divided by the separation of the two slits.

The light reflected from the upper surface of the thin film and the light reflected from the lower surface travel slightly different distances and interfere.

Only a transverse wave, in which the vibrations are at right angles to the direction of travel, can have those vibrations restricted to a single plane by a Polaroid.

Inserting a plate of thickness t in one arm makes the light cross it twice, so the extra path introduced is twice the thickness times the quantity refractive index minus one.

By the Rayleigh criterion the smallest angle the eye can resolve is 1.22 times the wavelength divided by the diameter of the pupil, that is 1.22 multiplied by 500 nanometres and divided by 3 millimetres, which comes to about 2.03 times ten to the power minus four radian.

Brewster found that when unpolarised light falls on a transparent surface at one particular angle of incidence, called the polarising angle, the reflected light is completely plane polarised, and at that angle the refractive index of the surface equals the tangent of the polarising angle.

In October 1962 American aerial photographs revealed Soviet missile sites under construction in Cuba; President John F. Kennedy ordered a naval quarantine of the island and, after thirteen days, Nikita Khrushchev agreed to withdraw the missiles, the United States undertaking not to invade Cuba.

The wall was opened and began to be broken up on 9 November 1989, the single most memorable image of the end of the Cold War.

The Gold Coast became independent as Ghana on 6 March 1957 under Kwame Nkrumah, the first colony in sub-Saharan Africa to do so, and Nkrumah became a leading voice of pan-Africanism and a founder of the Non-Aligned Movement.

Krishna Menon, India's best known diplomat of the period and later Defence Minister, is credited with coining the expression non-alignment in a United Nations speech in 1953; he is also remembered for the longest speech ever made at the Security Council, on Kashmir.

The five principles were written into the preamble of the agreement on trade and intercourse between India and the Tibet region of China, signed on 29 April 1954 by Jawaharlal Nehru and Zhou Enlai.

The first summit of non-aligned countries met at Belgrade, then the capital of Yugoslavia, in September 1961, with twenty-five participating countries, and Jawaharlal Nehru, Josip Broz Tito, Gamal Abdel Nasser, Sukarno and Kwame Nkrumah are regarded as the movement's founders.