UPSC Civil Services GK Questions 2026

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.

Patna University was set up on 1 October 1917 and is the oldest university in Bihar and among the oldest in the country; the oldest medical college of the state, Patna Medical College, followed in 1925.

Jairamdas Daulatram, a Congress leader and a member of the Constituent Assembly, was appointed the first Governor of Bihar after independence and later served as Governor of Assam and as a Union minister.

In the 2011 Census, Rohtas district, with its headquarters at Sasaram in the Patna division, recorded the highest literacy rate in Bihar, while Purnia recorded the lowest; the state average of about 61.8 per cent was the lowest among the states.

The Munger division, with its headquarters at Munger, has six districts: Munger, Jamui, Khagaria, Lakhisarai, Begusarai and Sheikhpura.

The Delhi Durbar of December 1911 announced the creation of a separate province, and it came into being on 22 March 1912 with its capital at Patna; the day is observed as Bihar Diwas.

Shri Krishna Sinha, remembered across the state as Shri Babu, was the first Chief Minister of Bihar and held the office for a long and formative period, during which the zamindari abolition legislation was taken up.

Arwal was carved out of Jehanabad district in 2001 and placed in the Magadh division. Its creation is important because Bihar was left with thirty-seven districts when Jharkhand was formed on 15 November 2000, and Arwal raised the number to the present thirty-eight.

Sheohar, a small district of the Tirhut division carved out of Sitamarhi, has the least area in the state and also the highest density of population, while Kaimur in the south-west has the lowest density.

West Champaran, whose headquarters is Bettiah and which lies in the Tirhut division along the border with Nepal, is the largest district of the state by area; the smallest by area is Sheohar, in the same division.

The Magadh division is administered from Gaya and contains the districts of Gaya, Jehanabad, Arwal, Nawada and Aurangabad.

The nine divisions are Patna, Magadh, Tirhut, Saran, Darbhanga, Kosi, Purnia, Bhagalpur and Munger, and the thirty-eight districts are distributed among them.

Thirteen hill districts were separated on 9 November 2000 to form the new state of Uttaranchal, which was renamed Uttarakhand in 2007, and Uttar Pradesh was left with seventy districts at that point.