RRB ALP GK Questions 2026

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.

Sound in air is a longitudinal wave, and only transverse waves can be polarised. Polarisation means restricting the vibrations of a wave to a single plane.

In the alkane series the boiling point rises as the carbon chain gets longer, and this order goes from 3 to 4 to 5 to 8 carbons.

The sulphide ion has 16 + 2 = 18 electrons, and its mass number of 32 is its count of nucleons.

With no work done, the first law of thermodynamics reduces to ΔU = Q, so the change in internal energy equals the heat that flows in or out.

The heat given out by 2 g of steam equals the heat taken in by 250 g of water, and that balance gives L = 550 Cal/g. The water warms from 20°C to 25°C, so it absorbs 250 × 1 × 5 = 1250 Cal.

Both statements are true, and the magnetic field set up by the current (Statement II) is exactly why the compass needle turns (Statement I).

The ball keeps slowing down by about 9.8 m/s every second until its speed becomes zero at the top, which takes 40 ÷ 9.8 ≈ 4 seconds.

Vision is caused by the electric field of light acting on the light-sensitive molecules of the retina. Light is an electromagnetic wave in which electric and magnetic fields oscillate at right angles to each other and to the direction of travel.

The energy gained is the charge of the electron multiplied by the potential difference it crosses. Energy W = qV.

The statement is Kirchhoff's voltage (loop) law, and it follows from the fact that energy is neither created nor destroyed.