RRB ALP GK Questions 2026

The speed of light in a medium is inversely proportional to its refractive index, so the ratio of speeds is the inverse ratio of the refractive indices.

Both particles gain the same kinetic energy, but the electron is far lighter, so it ends up much faster. When a charge q is accelerated through a potential difference V, it gains kinetic energy equal to qV.

Resistivity is a property of the material and its temperature, not of the wire's shape, so every copper wire has the same resistivity.

Sulphuric acid has two replaceable hydrogen atoms, so its equivalent mass is 98 ÷ 2 = 49 g, and 49 g in one litre makes exactly one gram-equivalent per litre.

Gravitational force varies inversely with the square of the distance, so doubling the distance cuts the force to one-fourth.

Kinetic energy equals p²/2m, so doubling the momentum p makes the kinetic energy four times as large. Momentum is p = mv and kinetic energy is KE = ½mv².

. Cathode rays behave the same whatever gas is in the tube, so the statement that they depend on the gas is not correct.

Ferromagnetism needs the atomic magnets of a substance to line up together in fixed regions called domains, and this happens only in the ordered structure of a solid.

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.

If the frequency of the soldiers' rhythmic steps happens to match the natural frequency of the bridge, the bridge is driven at its own frequency and its amplitude of vibration can build up to a dangerous level; breaking step destroys the rhythm and avoids the risk.